dash-docs/_includes/devdoc/ref_p2p_networking.md

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P2P Network

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This section describes the Dash P2P network protocol (but it is [not a specification][]). It does not describe the [BIP70 payment protocol][/en/glossary/payment-protocol], the [GetBlockTemplate mining protocol][section getblocktemplate], or any network protocol never implemented in an official version of Dash Core.

All peer-to-peer communication occurs entirely over TCP.

{% highlight text %} Note: unless their description says otherwise, all multi-byte integers mentioned in this section are transmitted in little-endian order. {% endhighlight %}

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Constants And Defaults

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The following constants and defaults are taken from Dash Core's [chainparams.cpp][core chainparams.cpp] source code file.

| Network | Default Port | Magic Value | [Start String][/en/glossary/start-string]{:#term-start-string}{:.term} | Max nBits |---------|--------------|-----------------------------------------------|--------------- | Mainnet | 9999 | 0xBD6B0CBF | 0xBF0C6BBD | 0x1e0ffff0 | Testnet | 19999 | 0xFFCAE2CE | 0xCEE2CAFF | 0x1e0ffff0 | Regtest | 19994 | 0xDCB7C1FC | 0xFCC1B7DC | 0x207fffff | Devnet | User-defined | 0xCEFFCAE2 | 0xE2CAFFCE | 0x207fffff

Note: the testnet start string and nBits above are for testnet3.

Command line parameters can change what port a node listens on (see -help). Start strings are hardcoded constants that appear at the start of all messages sent on the Dash network; they may also appear in data files such as Dash Core's block database. The Magic Value and nBits displayed above are in big-endian order; they're sent over the network in little-endian order. The Start String is simply the endian reversed Magic Value.

Dash Core's [chainparams.cpp][core chainparams.cpp] also includes other constants useful to programs, such as the hash of the genesis blocks for the different networks.

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Protocol Versions

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The table below lists some notable versions of the P2P network protocol, with the most recent versions listed first. (If you know of a protocol version that implemented a major change but which is not listed here, please [open an issue][docs issue].)

As of Dash Core 0.12.2.0, the most recent protocol version is 70208.

Version	Initial Release	Major Changes
70208	Dash Core 0.12.2.x (Nov 2017)	• DIP-0001 (2MB blocks) • Fee reduction (10x) • InstantSend fix • PrivateSend improvements • Experimental HD wallet • Local Masternode support removed
70206	Dash Core 0.12.1.x (Mar 2017)	• Switch to Bitcoin Core 0.12.1 • BIP-0065 (CheckLockTimeVerify) • BIP-0112 (CheckSequenceVerify)
70103	Dash Core 0.12.0.x (Aug 2015)	• Switch to Bitcoin Core 0.10 • Decentralized budget system • New IX implementation
70076	Dash Core 0.11.2.x (Mar 2015)	• Masternode enhancements • Mining/relay policy enhancements • BIP-66 - strict DER encoding for signatures
70066	Dash Core 0.11.1.x (Feb 2015)	• InstantX fully implemented • Spork fully implemented • Masternode payment updates • Rebrand to Dash (0.11.1.26)
70052	Dash Core 0.11.0.x (Jan 2015)	• Switch from fork of Litecoin 0.8 to Bitcoin 0.9.3 • Rebrand to Darkcoin Core
70051	Dash Core 0.10.0.x (Sep 2014)	• Release of the originally closed source implementation of DarkSend
70002	Dash Core 0.9.0.x (Mar 2014)	• Masternode implementation • Rebrand to Darkcoin
70002	Dash Core 0.8.7 (Jan 2014)	Initial release of Dash (branded XCoin) as a fork of Litecoin 0.8

Historical Bitcoin protocol versions for reference shown below since Dash is a fork of Bitcoin Core.

Version	Initial Release	Major Changes
70012	Bitcoin Core 0.12.0 (Feb 2016)	[BIP130][]: • Added sendheaders message.
70011	Bitcoin Core 0.12.0 (Feb 2016)	[BIP111][]: • filter* messages are disabled without NODE_BLOOM after and including this version.
70002	Bitcoin Core 0.9.0 (Mar 2014)	• Send multiple inv messages in response to a mempool message if necessary [BIP61][]: • Added reject message
70001	Bitcoin Core 0.8.0 (Feb 2013)	• Added notfound message. [BIP37][]: • Added filterload message. • Added filteradd message. • Added filterclear message. • Added merkleblock message. • Added relay field to version message • Added MSG_FILTERED_BLOCK inventory type to getdata message.
60002	Bitcoin Core 0.7.0 (Sep 2012)	[BIP35][]: • Added mempool message. • Extended getdata message to allow download of memory pool transactions
60001	Bitcoin Core 0.6.1 (May 2012)	[BIP31][]: • Added nonce field to ping message • Added pong message
60000	Bitcoin Core 0.6.0 (Mar 2012)	[BIP14][]: • Separated protocol version from Bitcoin Core version
31800	Bitcoin Core 0.3.18 (Dec 2010)	• Added getheaders message and headers message.
31402	Bitcoin Core 0.3.15 (Oct 2010)	• Added time field to addr message.
311	Bitcoin Core 0.3.11 (Aug 2010)	• Added alert message.
209	Bitcoin Core 0.2.9 (May 2010)	• Added checksum field to message headers.
106	Bitcoin Core 0.1.6 (Oct 2009)	• Added receive IP address fields to version message.

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Message Headers

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All messages in the network protocol use the same container format, which provides a required multi-field message header and an optional payload. The message header format is:

Bytes	Name	Data Type	Description
4	start string	char[4]	Magic bytes indicating the originating network; used to seek to next message when stream state is unknown.
12	command name	char[12]	ASCII string which identifies what message type is contained in the payload. Followed by nulls (0x00) to pad out byte count; for example: version\0\0\0\0\0.
4	payload size	uint32_t	Number of bytes in payload. The current maximum number of bytes ([MAX_SIZE][max_size]) allowed in the payload by Dash Core is 32 MiB---messages with a payload size larger than this will be dropped or rejected.
4	checksum	char[4]	Added in protocol version 209. First 4 bytes of SHA256(SHA256(payload)) in internal byte order. If payload is empty, as in verack and getaddr messages, the checksum is always 0x5df6e0e2 (SHA256(SHA256(<empty string>))).

The following example is an annotated hex dump of a mainnet message header from a verack message which has no payload.

{% highlight text %} bf0c6bbd ................... Start string: Mainnet 76657261636b000000000000 ... Command name: verack + null padding 00000000 ................... Byte count: 0 5df6e0e2 ................... Checksum: SHA256(SHA256()) {% endhighlight %}

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Data Messages

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The following network messages all request or provide data related to transactions and blocks.

Many of the data messages use [inventories][/en/glossary/inventory]{:#term-inventory}{:.term} as unique identifiers for transactions and blocks. Inventories have a simple 36-byte structure:

Bytes	Name	Data Type	Description
4	type identifier	uint32_t	The type of object which was hashed. See list of type identifiers below.
32	hash	char[32]	SHA256(SHA256()) hash of the object in internal byte order.

The currently-available type identifiers are:

Type Identifier	Name	Description
1	[MSG_TX][msg_tx]{:#term-msg_tx}{:.term}	The hash is a TXID.
2	[MSG_BLOCK][msg_block]{:#term-msg_block}{:.term}	The hash is of a block header.
3	[MSG_FILTERED_BLOCK][msg_filtered_block]{:#term-msg_filtered_block}{:.term}	The hash is of a block header; identical to MSG_BLOCK. When used in a getdata message, this indicates the response should be a merkleblock message rather than a block message (but this only works if a bloom filter was previously configured). Only for use in getdata messages.
4	[MSG_TXLOCK_REQUEST][msg_txlock_request]{:#term-msg_txlock_request}{:.term}	The hash is an Instant Send transaction lock request.
5	[MSG_TXLOCK_VOTE][msg_txlock_vote]{:#term-msg_txlock_vote}{:.term}	The hash is an Instant Send transaction vote.
6	[MSG_SPORK][msg_spork]{:#term-msg_spork}{:.term}	The hash is Spork ID.
7	[MSG_MASTERNODE_PAYMENT_VOTE][msg_masternode_payment_vote]{:#term-msg_masternode_payment_vote}{:.term}	The hash is a Masternode Payment Vote.
8	[MSG_MASTERNODE_PAYMENT_BLOCK][msg_masternode_payment_block]{:#term-msg_masternode_payment_block}{:.term}	The hash is a Masternode Payment Block.
8	MSG_MASTERNODE_SCANNING_ERROR	Replaced by MSG_MASTERNODE_PAYMENT_BLOCK
9	[MSG_BUDGET_VOTE][msg_budget_vote]{:#term-msg_budget_vote}{:.term}	Deprecated
10	[MSG_BUDGET_PROPOSAL][msg_budget_proposal]{:#term-msg_budget_proposal}{:.term}	Deprecated
11	[MSG_BUDGET_FINALIZED][msg_budget_finalized]{:#term-msg_budget_finalized}{:.term}	Deprecated
12	[MSG_BUDGET_FINALIZED_VOTE][msg_budget_finalized_vote]{:#term-msg_budget_finalized_vote}{:.term}	Deprecated
13	[MSG_MASTERNODE_QUORUM][msg_masternode_quorum]{:#term-msg_masternode_quorum}{:.term}	Not Implemented
14	[MSG_MASTERNODE_ANNOUNCE][msg_masternode_announce]{:#term-msg_masternode_announce}{:.term}	The hash is a Masternode Broadcast.
15	[MSG_MASTERNODE_PING][msg_masternode_ping]{:#term-msg_masternode_ping}{:.term}	The hash is a Masternode Ping.
16	[MSG_DSTX][msg_dstx]{:#term-msg_dstx}{:.term}	The hash is Private Send (Dark Send) Broadcast TX.
17	[MSG_GOVERNANCE_OBJECT][msg_governance_object]{:#term-msg_governance_object}{:.term}	The hash is a Governance Object.
18	[MSG_GOVERNANCE_OBJECT_VOTE][msg_governance_object_vote]{:#term-msg_governance_object_vote}{:.term}	The hash is a Governance Object Vote.
19	[MSG_MASTERNODE_VERIFY][msg_masternode_verify]{:#term-msg_masternode_verify}{:.term}	The hash is a Masternode Verify.
20	[MSG_CMPCT_BLOCK][msg_cmpct_block]{:#term-msg_cmpct_block}{:.term}	The hash is of a compact block.

Type identifier zero and type identifiers greater than twenty are reserved for future implementations. Dash Core ignores all inventories with one of these unknown types.

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Block

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The block message transmits a single serialized block in the format described in the [serialized blocks section][section serialized blocks]. See that section for an example hexdump. It can be sent for two different reasons:

1. GetData Response: Nodes will always send it in response to a getdata message that requests the block with an inventory type of MSG_BLOCK (provided the node has that block available for relay).

2. Unsolicited: Some miners will send unsolicited block messages broadcasting their newly-mined blocks to all of their peers. Many mining pools do the same thing, although some may be misconfigured to send the block from multiple nodes, possibly sending the same block to some peers more than once.

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Blocktxn

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Added in protocol version 70209 of Dash Core.

The blocktxn message sends requested block transactions to a node which previously requested them with a getblocktxn message.

Bytes	Name	Data Type	Encoding	Description
32	blockhash	Binary blob	The output from a double-SHA256 of the block header, as used elsewhere	The blockhash of the block which the transactions being provided are in
1 or 3	transactions_length	CompactSize	As used to encode array lengths elsewhere	The number of transactions provided
variable	transactions	List of transactions	As encoded in tx messages in response to getdata MSG_TX	The transactions provided

The following annotated hexdump shows a blocktxn message. (The message header has been omitted.)

{% highlight text %} ADD HEXDUMP HERE {% endhighlight %}

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CmpctBlock

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The cmpctblock message transmits a single serialized compact block.

ADD DESCRIPTION, FORMAT, AND HEXDUMP

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GetBlocks

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The getblocks message requests an inv message that provides block header hashes starting from a particular point in the block chain. It allows a peer which has been disconnected or started for the first time to get the data it needs to request the blocks it hasn't seen.

Peers which have been disconnected may have stale blocks in their locally-stored block chain, so the getblocks message allows the requesting peer to provide the receiving peer with multiple header hashes at various heights on their local chain. This allows the receiving peer to find, within that list, the last header hash they had in common and reply with all subsequent header hashes.

Note: the receiving peer itself may respond with an inv message containing header hashes of stale blocks. It is up to the requesting peer to poll all of its peers to find the best block chain.

If the receiving peer does not find a common header hash within the list, it will assume the last common block was the genesis block (block zero), so it will reply with in inv message containing header hashes starting with block one (the first block after the genesis block).

Bytes	Name	Data Type	Description
4	version	uint32_t	The protocol version number; the same as sent in the version message.
Varies	hash count	compactSize uint	The number of header hashes provided not including the stop hash. There is no limit except that the byte size of the entire message must be below the [MAX_SIZE][max_size] limit; typically from 1 to 200 hashes are sent.
Varies	block header hashes	char[32]	One or more block header hashes (32 bytes each) in internal byte order. Hashes should be provided in reverse order of block height, so highest-height hashes are listed first and lowest-height hashes are listed last.
32	stop hash	char[32]	The header hash of the last header hash being requested; set to all zeroes to request an inv message with all subsequent header hashes (a maximum of 500 will be sent as a reply to this message; if you need more than 500, you will need to send another getblocks message with a higher-height header hash as the first entry in block header hash field).

The following annotated hexdump shows a getblocks message. (The message header has been omitted.)

{% highlight text %} 71110100 ........................... Protocol version: 70001 02 ................................. Hash count: 2

d39f608a7775b537729884d4e6633bb2 105e55a16a14d31b0000000000000000 ... Hash #1

5c3e6403d40837110a2e8afb602b1c01 714bda7ce23bea0a0000000000000000 ... Hash #2

00000000000000000000000000000000 00000000000000000000000000000000 ... Stop hash {% endhighlight %}

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GetBlockTxn

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Added in protocol version 70209 of Dash Core.

The getblocktxn message requests a blocktxn message for any transactions that it has not seen after a compact block is received.

Bytes	Name	Data Type	Encoding	Description
32	blockhash	Binary blob	The output from a double-SHA256 of the block header, as used elsewhere	The blockhash of the block which the transactions being requested are in
1 or 3	indexes_length	CompactSize	As used to encode array lengths elsewhere	The number of transactions requested
(1 or 3) * indexes_length	indexes	List of CompactSizes	Differentially encoded	The indexes of the transactions being requested in the block

The following annotated hexdump shows a getblocktxn message. (The message header has been omitted.)

{% highlight text %} ADD HEXDUMP HERE {% endhighlight %}

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GetData

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The getdata message requests one or more data objects from another node. The objects are requested by an inventory, which the requesting node typically previously received by way of an inv message.

The response to a getdata message can be a tx message, block message, merkleblock message, ix message, txlvote message, mnw message, mnb message, mnp message, dstx message, govobj message, govobjvote message, mnv message, or notfound message.

This message cannot be used to request arbitrary data, such as historic transactions no longer in the memory pool or relay set. Full nodes may not even be able to provide older blocks if they've pruned old transactions from their block database. For this reason, the getdata message should usually only be used to request data from a node which previously advertised it had that data by sending an inv message.

The format and maximum size limitations of the getdata message are identical to the inv message; only the message header differs.

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GetHeaders

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Added in protocol version 70077.

The getheaders message requests a headers message that provides block headers starting from a particular point in the block chain. It allows a peer which has been disconnected or started for the first time to get the headers it hasn’t seen yet.

The getheaders message is nearly identical to the getblocks message, with one minor difference: the inv reply to the getblocks message will include no more than 500 block header hashes; the headers reply to the getheaders message will include as many as 2,000 block headers.

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Headers

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Added in protocol version 31800 (of Bitcoin).

The headers message sends block headers to a node which previously requested certain headers with a getheaders message. A headers message can be empty.

Bytes	Name	Data Type	Description
Varies	count	compactSize uint	Number of block headers up to a maximum of 2,000. Note: headers-first sync assumes the sending node will send the maximum number of headers whenever possible.
Varies	headers	block_header	Block headers: each 80-byte block header is in the format described in the [block headers section][section block header] with an additional 0x00 suffixed. This 0x00 is called the transaction count, but because the headers message doesn't include any transactions, the transaction count is always zero.

The following annotated hexdump shows a headers message. (The message header has been omitted.)

{% highlight text %} 01 ................................. Header count: 1

02000000 ........................... Block version: 2 b6ff0b1b1680a2862a30ca44d346d9e8 910d334beb48ca0c0000000000000000 ... Hash of previous block's header 9d10aa52ee949386ca9385695f04ede2 70dda20810decd12bc9b048aaab31471 ... Merkle root 24d95a54 ........................... Unix time: 1415239972 30c31b18 ........................... Target (bits) fe9f0864 ........................... Nonce

00 ................................. Transaction count (0x00) {% endhighlight %}

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Inv

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The inv message (inventory message) transmits one or more inventories of objects known to the transmitting peer. It can be sent unsolicited to announce new transactions or blocks, or it can be sent in reply to a getblocks message or mempool message.

The receiving peer can compare the inventories from an inv message against the inventories it has already seen, and then use a follow-up message to request unseen objects.

Bytes	Name	Data Type	Description
Varies	count	compactSize uint	The number of inventory entries.
Varies	inventory	inventory	One or more inventory entries up to a maximum of 50,000 entries.

The following annotated hexdump shows an inv message with two inventory entries. (The message header has been omitted.)

{% highlight text %} 02 ................................. Count: 2

0f000000 ........................... Type: MSG_MASTERNODE_PING dd6cc6c11211793b239c2e311f1496e2 2281b200b35233eaae465d2aa3c9d537 ... Hash (mnp)

05000000 ........................... Type: MSG_TXLOCK_VOTE afc5b2f418f8c06c477a7d071240f5ee ab17057f9ce4b50c2aef4fadf3729a2e ... Hash (txlvote) {% endhighlight %}

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MemPool

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Added in protocol version 60002 (of Bitcoin).

The mempool message requests the TXIDs of transactions that the receiving node has verified as valid but which have not yet appeared in a block. That is, transactions which are in the receiving node's memory pool. The response to the mempool message is one or more inv messages containing the TXIDs in the usual inventory format.

Sending the mempool message is mostly useful when a program first connects to the network. Full nodes can use it to quickly gather most or all of the unconfirmed transactions available on the network; this is especially useful for miners trying to gather transactions for their transaction fees. SPV clients can set a filter before sending a mempool to only receive transactions that match that filter; this allows a recently-started client to get most or all unconfirmed transactions related to its wallet.

The inv response to the mempool message is, at best, one node's view of the network---not a complete list of unconfirmed transactions on the network. Here are some additional reasons the list might not be complete:

• Before Bitcoin Core 0.9.0, the response to the mempool message was only one inv message. An inv message is limited to 50,000 inventories, so a node with a memory pool larger than 50,000 entries would not send everything. Later versions of Bitcoin Core send as many inv messages as needed to reference its complete memory pool.

• The mempool message is not currently fully compatible with the filterload message's BLOOM_UPDATE_ALL and BLOOM_UPDATE_P2PUBKEY_ONLY flags. Mempool transactions are not sorted like in-block transactions, so a transaction (tx2) spending an output can appear before the transaction (tx1) containing that output, which means the automatic filter update mechanism won't operate until the second-appearing transaction (tx1) is seen---missing the first-appearing transaction (tx2). It has been proposed in [Bitcoin Core issue #2381][] that the transactions should be sorted before being processed by the filter.

There is no payload in a mempool message. See the [message header section][section message header] for an example of a message without a payload.

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MerkleBlock

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Added in protocol version 70001 as described by BIP37.

The merkleblock message is a reply to a getdata message which requested a block using the inventory type MSG_MERKLEBLOCK. It is only part of the reply: if any matching transactions are found, they will be sent separately as tx messages.

If a filter has been previously set with the filterload message, the merkleblock message will contain the TXIDs of any transactions in the requested block that matched the filter, as well as any parts of the block's merkle tree necessary to connect those transactions to the block header's merkle root. The message also contains a complete copy of the block header to allow the client to hash it and confirm its proof of work.

Bytes	Name	Data Type	Description
80	block header	block_header	The block header in the format described in the [block header section][section block header].
4	transaction count	uint32_t	The number of transactions in the block (including ones that don't match the filter).
Varies	hash count	compactSize uint	The number of hashes in the following field.
Varies	hashes	char[32]	One or more hashes of both transactions and merkle nodes in internal byte order. Each hash is 32 bytes.
Varies	flag byte count	compactSize uint	The number of flag bytes in the following field.
Varies	flags	byte[]	A sequence of bits packed eight in a byte with the least significant bit first. May be padded to the nearest byte boundary but must not contain any more bits than that. Used to assign the hashes to particular nodes in the merkle tree as described below.

The annotated hexdump below shows a merkleblock message which corresponds to the examples below. (The message header has been omitted.)

{% highlight text %} 01000000 ........................... Block version: 1 82bb869cf3a793432a66e826e05a6fc3 7469f8efb7421dc88067010000000000 ... Hash of previous block's header 7f16c5962e8bd963659c793ce370d95f 093bc7e367117b3c30c1f8fdd0d97287 ... Merkle root 76381b4d ........................... Time: 1293629558 4c86041b ........................... nBits: 0x04864c * 256**(0x1b-3) 554b8529 ........................... Nonce

07000000 ........................... Transaction count: 7 04 ................................. Hash count: 4

3612262624047ee87660be1a707519a4 43b1c1ce3d248cbfc6c15870f6c5daa2 ... Hash #1 019f5b01d4195ecbc9398fbf3c3b1fa9 bb3183301d7a1fb3bd174fcfa40a2b65 ... Hash #2 41ed70551dd7e841883ab8f0b16bf041 76b7d1480e4f0af9f3d4c3595768d068 ... Hash #3 20d2a7bc994987302e5b1ac80fc425fe 25f8b63169ea78e68fbaaefa59379bbf ... Hash #4

01 ................................. Flag bytes: 1 1d ................................. Flags: 1 0 1 1 1 0 0 0 {% endhighlight %}

Note: when fully decoded, the above merkleblock message provided the TXID for a single transaction that matched the filter. In the network traffic dump this output was taken from, the full transaction belonging to that TXID was sent immediately after the merkleblock message as a tx message.

Parsing A MerkleBlock Message

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As seen in the annotated hexdump above, the merkleblock message provides three special data types: a transaction count, a list of hashes, and a list of one-bit flags.

You can use the transaction count to construct an empty merkle tree. We'll call each entry in the tree a node; on the bottom are TXID nodes---the hashes for these nodes are TXIDs; the remaining nodes (including the merkle root) are non-TXID nodes---they may actually have the same hash as a TXID, but we treat them differently.

Keep the hashes and flags in the order they appear in the merkleblock message. When we say "next flag" or "next hash", we mean the next flag or hash on the list, even if it's the first one we've used so far.

Start with the merkle root node and the first flag. The table below describes how to evaluate a flag based on whether the node being processed is a TXID node or a non-TXID node. Once you apply a flag to a node, never apply another flag to that same node or reuse that same flag again.

Flag	TXID Node	Non-TXID Node
0	Use the next hash as this node's TXID, but this transaction didn't match the filter.	Use the next hash as this node's hash. Don't process any descendant nodes.
1	Use the next hash as this node's TXID, and mark this transaction as matching the filter.	The hash needs to be computed. Process the left child node to get its hash; process the right child node to get its hash; then concatenate the two hashes as 64 raw bytes and hash them to get this node's hash.

Any time you begin processing a node for the first time, evaluate the next flag. Never use a flag at any other time.

When processing a child node, you may need to process its children (the grandchildren of the original node) or further-descended nodes before returning to the parent node. This is expected---keep processing depth first until you reach a TXID node or a non-TXID node with a flag of 0.

After you process a TXID node or a non-TXID node with a flag of 0, stop processing flags and begin to ascend the tree. As you ascend, compute the hash of any nodes for which you now have both child hashes or for which you now have the sole child hash. See the [merkle tree section][section merkle trees] for hashing instructions. If you reach a node where only the left hash is known, descend into its right child (if present) and further descendants as necessary.

However, if you find a node whose left and right children both have the same hash, fail. This is related to CVE-2012-2459.

Continue descending and ascending until you have enough information to obtain the hash of the merkle root node. If you run out of flags or hashes before that condition is reached, fail. Then perform the following checks (order doesn't matter):

• Fail if there are unused hashes in the hashes list.

• Fail if there are unused flag bits---except for the minimum number of bits necessary to pad up to the next full byte.

• Fail if the hash of the merkle root node is not identical to the merkle root in the block header.

• Fail if the block header is invalid. Remember to ensure that the hash of the header is less than or equal to the target threshold encoded by the nBits header field. Your program should also, of course, attempt to ensure the header belongs to the best block chain and that the user knows how many confirmations this block has.

For a detailed example of parsing a merkleblock message, please see the corresponding [merkle block examples section][section merkleblock example].

Creating A MerkleBlock Message

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It's easier to understand how to create a merkleblock message after you understand how to parse an already-created message, so we recommend you read the parsing section above first.

Create a complete merkle tree with TXIDs on the bottom row and all the other hashes calculated up to the merkle root on the top row. For each transaction that matches the filter, track its TXID node and all of its ancestor nodes.

Start processing the tree with the merkle root node. The table below describes how to process both TXID nodes and non-TXID nodes based on whether the node is a match, a match ancestor, or neither a match nor a match ancestor.

	TXID Node	Non-TXID Node
Neither Match Nor Match Ancestor	Append a 0 to the flag list; append this node's TXID to the hash list.	Append a 0 to the flag list; append this node's hash to the hash list. Do not descend into its child nodes.
Match Or Match Ancestor	Append a 1 to the flag list; append this node's TXID to the hash list.	Append a 1 to the flag list; process the left child node. Then, if the node has a right child, process the right child. Do not append a hash to the hash list for this node.

Any time you begin processing a node for the first time, a flag should be appended to the flag list. Never put a flag on the list at any other time, except when processing is complete to pad out the flag list to a byte boundary.

When processing a child node, you may need to process its children (the grandchildren of the original node) or further-descended nodes before returning to the parent node. This is expected---keep processing depth first until you reach a TXID node or a node which is neither a TXID nor a match ancestor.

After you process a TXID node or a node which is neither a TXID nor a match ancestor, stop processing and begin to ascend the tree until you find a node with a right child you haven't processed yet. Descend into that right child and process it.

After you fully process the merkle root node according to the instructions in the table above, processing is complete. Pad your flag list to a byte boundary and construct the merkleblock message using the template near the beginning of this subsection.

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NotFound

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Added in protocol version 70001.

The notfound message is a reply to a getdata message which requested an object the receiving node does not have available for relay. (Nodes are not expected to relay historic transactions which are no longer in the memory pool or relay set. Nodes may also have pruned spent transactions from older blocks, making them unable to send those blocks.)

The format and maximum size limitations of the notfound message are identical to the inv message; only the message header differs.

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Tx

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The tx message transmits a single transaction in the raw transaction format. It can be sent in a variety of situations;

• Transaction Response: Dash Core will send it in response to a getdata message that requests the transaction with an inventory type of MSG_TX.

• MerkleBlock Response: Dash Core will send it in response to a getdata message that requests a merkle block with an inventory type of MSG_MERKLEBLOCK. (This is in addition to sending a merkleblock message.) Each tx message in this case provides a matched transaction from that block.

For an example hexdump of the raw transaction format, see the [raw transaction section][raw transaction format].

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Control Messages

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The following network messages all help control the connection between two peers or allow them to advise each other about the rest of the network.

Note that almost none of the control messages are authenticated in any way, meaning they can contain incorrect or intentionally harmful information. In addition, this section does not yet cover P2P protocol operation over the [Tor network][tor]; if you would like to contribute information about Tor, please [open an issue][docs issue].

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Addr

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The addr (IP address) message relays connection information for peers on the network. Each peer which wants to accept incoming connections creates an addr message providing its connection information and then sends that message to its peers unsolicited. Some of its peers send that information to their peers (also unsolicited), some of which further distribute it, allowing decentralized peer discovery for any program already on the network.

An addr message may also be sent in response to a getaddr message.

Bytes	Name	Data Type	Description
Varies	IP address count	compactSize uint	The number of IP address entries up to a maximum of 1,000.
Varies	IP addresses	network IP address	IP address entries. See the table below for the format of a Dash network IP address.

Each encapsulated network IP address currently uses the following structure:

Bytes	Name	Data Type	Description
4	time	uint32	Added in protocol version 31402. A time in Unix epoch time format. Nodes advertising their own IP address set this to the current time. Nodes advertising IP addresses they've connected to set this to the last time they connected to that node. Other nodes just relaying the IP address should not change the time. Nodes can use the time field to avoid relaying old addr messages. Malicious nodes may change times or even set them in the future.
8	services	uint64_t	The services the node advertised in its version message.
16	IP address	char	IPv6 address in big endian byte order. IPv4 addresses can be provided as [IPv4-mapped IPv6 addresses][]
2	port	uint16_t	Port number in big endian byte order. Note that Dash Core will only connect to nodes with non-standard port numbers as a last resort for finding peers. This is to prevent anyone from trying to use the network to disrupt non-Dash services that run on other ports.

The following annotated hexdump shows part of an addr message. (The message header has been omitted and the actual IP address has been replaced with a [RFC5737][] reserved IP address.)

{% highlight text %} fde803 ............................. Address count: 1000

d91f4854 ........................... Epoch time: 1414012889 0100000000000000 ................... Service bits: 01 (network node) 00000000000000000000ffffc0000233 ... IP Address: ::ffff:192.0.2.51 208d ............................... Port: 8333

[...] .............................. (999 more addresses omitted) {% endhighlight %}

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Alert

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Added in protocol version 311. Removed by Bitcoin in protocol version 70013, but retained by Dash.

The alert message warns nodes of problems that may affect them or the rest of the network. Each alert message is signed using a key controlled by respected community members, mostly Dash Core developers.

To ensure all nodes can validate and forward alert messages, encapsulation is used. Developers create an alert using the data structure appropriate for the versions of the software they want to notify; then they serialize that data and sign it. The serialized data and its signature make up the outer alert message---allowing nodes which don't understand the data structure to validate the signature and relay the alert to nodes which do understand it. The nodes which actually need the message can decode the serialized data to access the inner alert message.

The outer alert message has four fields:

Bytes	Name	Data Type	Description
Variable	alert bytes	compactSize uint	The number of bytes in following alert field.
Variable	alert	uchar	The serialized alert. See below for a description of the current alert format.
Variable	signature bytes	compactSize uint	The number of bytes in the following signature field.
Variable	signature	uchar	A DER-encoded ECDSA (secp256k1) signature of the alert signed with the developer's alert key.

Although designed to be easily upgraded, the format of the inner serialized alert has not changed since the alert message was first introduced in protocol version 311.

Bytes	Name	Data Type	Description
4	version	int32_t	Alert format version. Version 1 from protocol version 311 through at least protocol version 70002.
8	relayUntil	int64_t	The time beyond which nodes should stop relaying this alert. Unix epoch time format.
8	expiration	int64_t	The time beyond which this alert is no longer in effect and should be ignored. Unix epoch time format.
4	ID	int32_t	A unique ID number for this alert.
4	cancel	int32_t	All alerts with an ID number less than or equal to this number should be canceled: deleted and not accepted in the future.
Varies	setCancel count	compactSize uint	The number of IDs in the following setCancel field. May be zero.
Varies	setCancel	int32_t	Alert IDs which should be canceled. Each alert ID is a separate int32_t number.
4	minVer	int32_t	This alert only applies to protocol versions greater than or equal to this version. Nodes running other protocol versions should still relay it.
4	maxVer	int32_t	This alert only applies to protocol versions less than or equal to this version. Nodes running other protocol versions should still relay it.
Varies	user_agent count	compactSize uint	The number of user agent strings in the following setUser_agent field. May be zero.
Varies	setUser_agent	compactSize uint + string	If this field is empty, it has no effect on the alert. If there is at least one entry is this field, this alert only applies to programs with a user agent that exactly matches one of the strings in this field. Each entry in this field is a compactSize uint followed by a string---the uint indicates how many bytes are in the following string. This field was originally called setSubVer; since BIP14, it applies to user agent strings as defined in the version message.
4	priority	int32_t	Relative priority compared to other alerts.
Varies	comment bytes	compactSize uint	The number of bytes in the following comment field. May be zero.
Varies	comment	string	A comment on the alert that is not displayed.
Varies	statusBar bytes	compactSize uint	The number of bytes in the following statusBar field. May be zero.
Varies	statusBar	string	The alert message that is displayed to the user.
Varies	reserved bytes	compactSize uint	The number of bytes in the following reserved field. May be zero.
Varies	reserved	string	Reserved for future use. Originally called RPC Error.

The annotated hexdump below shows an alert message. (The message header has been omitted.)

{% highlight text %} 73 ................................. Bytes in encapsulated alert: 115 01000000 ........................... Version: 1 3766404f00000000 ................... RelayUntil: 1329620535 b305434f00000000 ................... Expiration: 1330917376

f2030000 ........................... ID: 1010 f1030000 ........................... Cancel: 1009 00 ................................. setCancel count: 0

10270000 ........................... MinVer: 10000 48ee0000 ........................... MaxVer: 61000 00 ................................. setUser_agent bytes: 0 64000000 ........................... Priority: 100

00 ................................. Bytes In Comment String: 0 46 ................................. Bytes in StatusBar String: 70 53656520626974636f696e2e6f72672f 666562323020696620796f7520686176 652074726f75626c6520636f6e6e6563 74696e67206166746572203230204665 627275617279 ....................... Status Bar String: "See [...]" 00 ................................. Bytes In Reserved String: 0

47 ................................. Bytes in signature: 71 30450221008389df45f0703f39ec8c1c c42c13810ffcae14995bb648340219e3 53b63b53eb022009ec65e1c1aaeec1fd 334c6b684bde2b3f573060d5b70c3a46 723326e4e8a4f1 ..................... Signature {% endhighlight %}

Alert key compromise: Dash Core's source code defines a particular set of alert parameters that can be used to notify users that the alert signing key has been compromised and that they should upgrade to get a new alert public key. Once a signed alert containing those parameters has been received, no other alerts can cancel or override it. See the ProcessAlert() function in the Dash Core [alert.cpp][core alert.cpp] source code for the parameters of this message.

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FilterAdd

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Added in protocol version 70001 as described by BIP37.

The filteradd message tells the receiving peer to add a single element to a previously-set bloom filter, such as a new public key. The element is sent directly to the receiving peer; the peer then uses the parameters set in the filterload message to add the element to the bloom filter.

Because the element is sent directly to the receiving peer, there is no obfuscation of the element and none of the plausible-deniability privacy provided by the bloom filter. Clients that want to maintain greater privacy should recalculate the bloom filter themselves and send a new filterload message with the recalculated bloom filter.

Bytes	Name	Data Type	Description
Varies	element bytes	compactSize uint	The number of bytes in the following element field.
Varies	element	uint8_t[]	The element to add to the current filter. Maximum of 520 bytes, which is the maximum size of an element which can be pushed onto the stack in a pubkey or signature script. Elements must be sent in the byte order they would use when appearing in a raw transaction; for example, hashes should be sent in internal byte order.

Note: a filteradd message will not be accepted unless a filter was previously set with the filterload message.

The annotated hexdump below shows a filteradd message adding a TXID. (The message header has been omitted.) This TXID appears in the same block used for the example hexdump in the merkleblock message; if that merkleblock message is re-sent after sending this filteradd message, six hashes are returned instead of four.

{% highlight text %} 20 ................................. Element bytes: 32 fdacf9b3eb077412e7a968d2e4f11b9a 9dee312d666187ed77ee7d26af16cb0b ... Element (A TXID) {% endhighlight %}

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FilterClear

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Added in protocol version 70001 as described by BIP37.

The filterclear message tells the receiving peer to remove a previously-set bloom filter. This also undoes the effect of setting the relay field in the version message to 0, allowing unfiltered access to inv messages announcing new transactions.

Dash Core does not require a filterclear message before a replacement filter is loaded with filterload. It also doesn't require a filterload message before a filterclear message.

There is no payload in a filterclear message. See the [message header section][section message header] for an example of a message without a payload.

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FilterLoad

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Added in protocol version 70001 as described by BIP37.

The filterload message tells the receiving peer to filter all relayed transactions and requested merkle blocks through the provided filter. This allows clients to receive transactions relevant to their wallet plus a configurable rate of false positive transactions which can provide plausible-deniability privacy.

Bytes	Name	Data Type	Description
Varies	nFilterBytes	compactSize uint	Number of bytes in the following filter bit field.
Varies	filter	uint8_t[]	A bit field of arbitrary byte-aligned size. The maximum size is 36,000 bytes.
4	nHashFuncs	uint32_t	The number of hash functions to use in this filter. The maximum value allowed in this field is 50.
4	nTweak	uint32_t	An arbitrary value to add to the seed value in the hash function used by the bloom filter.
1	nFlags	uint8_t	A set of flags that control how outpoints corresponding to a matched pubkey script are added to the filter. See the table in the Updating A Bloom Filter subsection below.

The annotated hexdump below shows a filterload message. (The message header has been omitted.) For an example of how this payload was created, see the [filterload example][section creating a bloom filter].

{% highlight text %} 02 ......... Filter bytes: 2 b50f ....... Filter: 1010 1101 1111 0000 0b000000 ... nHashFuncs: 11 00000000 ... nTweak: 0/none 00 ......... nFlags: BLOOM_UPDATE_NONE {% endhighlight %}

Initializing A Bloom Filter

Filters have two core parameters: the size of the bit field and the number of hash functions to run against each data element. The following formulas from BIP37 will allow you to automatically select appropriate values based on the number of elements you plan to insert into the filter (n) and the false positive rate (p) you desire to maintain plausible deniability.

• Size of the bit field in bytes (nFilterBytes), up to a maximum of 36,000: (-1 / log(2)**2 * n * log(p)) / 8

• Hash functions to use (nHashFuncs), up to a maximum of 50: nFilterBytes * 8 / n * log(2)

Note that the filter matches parts of transactions (transaction elements), so the false positive rate is relative to the number of elements checked---not the number of transactions checked. Each normal transaction has a minimum of four matchable elements (described in the comparison subsection below), so a filter with a false-positive rate of 1 percent will match about 4 percent of all transactions at a minimum.

According to BIP37, the formulas and limits described above provide support for bloom filters containing 20,000 items with a false positive rate of less than 0.1 percent or 10,000 items with a false positive rate of less than 0.0001 percent.

Once the size of the bit field is known, the bit field should be initialized as all zeroes.

Populating A Bloom Filter

The bloom filter is populated using between 1 and 50 unique hash functions (the number specified per filter by the nHashFuncs field). Instead of using up to 50 different hash function implementations, a single implementation is used with a unique seed value for each function.

The seed is nHashNum * 0xfba4c795 + nTweak as a uint32_t, where the values are:

• nHashNum is the sequence number for this hash function, starting at 0 for the first hash iteration and increasing up to the value of the nHashFuncs field (minus one) for the last hash iteration.

• 0xfba4c795 is a constant optimized to create large differences in the seed for different values of nHashNum.

• nTweak is a per-filter constant set by the client to require the use of an arbitrary set of hash functions.

If the seed resulting from the formula above is larger than four bytes, it must be truncated to its four most significant bytes (for example, 0x8967452301 & 0xffffffff → 0x67452301).

The actual hash function implementation used is the [32-bit Murmur3 hash function][murmur3].

Warning: the Murmur3 hash function has separate 32-bit and 64-bit versions that produce different results for the same input. Only the 32-bit Murmur3 version is used with Dash bloom filters.

The data to be hashed can be any transaction element which the bloom filter can match. See the next subsection for the list of transaction elements checked against the filter. The largest element which can be matched is a script data push of 520 bytes, so the data should never exceed 520 bytes.

The example below from Dash Core [bloom.cpp][core bloom.cpp hash] combines all the steps above to create the hash function template. The seed is the first parameter; the data to be hashed is the second parameter. The result is a uint32_t modulo the size of the bit field in bits.

{% highlight c++ %} MurmurHash3(nHashNum * 0xFBA4C795 + nTweak, vDataToHash) % (vData.size() * 8) {% endhighlight %}

Each data element to be added to the filter is hashed by nHashFuncs number of hash functions. Each time a hash function is run, the result will be the index number (nIndex) of a bit in the bit field. That bit must be set to 1. For example if the filter bit field was 00000000 and the result is 5, the revised filter bit field is 00000100 (the first bit is bit 0).

It is expected that sometimes the same index number will be returned more than once when populating the bit field; this does not affect the algorithm---after a bit is set to 1, it is never changed back to 0.

After all data elements have been added to the filter, each set of eight bits is converted into a little-endian byte. These bytes are the value of the filter field.

Comparing Transaction Elements To A Bloom Filter

To compare an arbitrary data element against the bloom filter, it is hashed using the same parameters used to create the bloom filter. Specifically, it is hashed nHashFuncs times, each time using the same nTweak provided in the filter, and the resulting output is modulo the size of the bit field provided in the filter field. After each hash is performed, the filter is checked to see if the bit at that indexed location is set. For example if the result of a hash is 5 and the filter is 01001110, the bit is considered set.

If the result of every hash points to a set bit, the filter matches. If any of the results points to an unset bit, the filter does not match.

The following transaction elements are compared against bloom filters. All elements will be hashed in the byte order used in blocks (for example, TXIDs will be in internal byte order).

• TXIDs: the transaction's SHA256(SHA256()) hash.

• Outpoints: each 36-byte outpoint used this transaction's input section is individually compared to the filter.

• Signature Script Data: each element pushed onto the stack by a data-pushing opcode in a signature script from this transaction is individually compared to the filter. This includes data elements present in P2SH redeem scripts when they are being spent.

• PubKey Script Data: each element pushed onto the the stack by a data-pushing opcode in any pubkey script from this transaction is individually compared to the filter. (If a pubkey script element matches the filter, the filter will be immediately updated if the BLOOM_UPDATE_ALL flag was set; if the pubkey script is in the P2PKH format and matches the filter, the filter will be immediately updated if the BLOOM_UPDATE_P2PUBKEY_ONLY flag was set. See the subsection below for details.)

The following annotated hexdump of a transaction is from the [raw transaction format section][raw transaction format]; the elements which would be checked by the filter are emphasized in bold. Note that this transaction's TXID (01000000017b1eab[...]) would also be checked, and that the outpoint TXID and index number below would be checked as a single 36-byte element.

01000000 ................................... Version

01 ......................................... Number of inputs
|
| 7b1eabe0209b1fe794124575ef807057
| c77ada2138ae4fa8d6c4de0398a14f3f ......... Outpoint TXID
| 00000000 ................................. Outpoint index number
|
| 49 ....................................... Bytes in sig. script: 73
| | 48 ..................................... Push 72 bytes as data
| | | 30450221008949f0cb400094ad2b5eb3
| | | 99d59d01c14d73d8fe6e96df1a7150de
| | | b388ab8935022079656090d7f6bac4c9
| | | a94e0aad311a4268e082a725f8aeae05
| | | 73fb12ff866a5f01 ..................... Secp256k1 signature
|
| ffffffff ................................. Sequence number: UINT32_MAX

01 ......................................... Number of outputs
| f0ca052a01000000 ......................... Satoshis (49.99990000 BTC)
|
| 19 ....................................... Bytes in pubkey script: 25
| | 76 ..................................... OP_DUP
| | a9 ..................................... OP_HASH160
| | 14 ..................................... Push 20 bytes as data
| | | cbc20a7664f2f69e5355aa427045bc15
| | | e7c6c772 ............................. PubKey hash
| | 88 ..................................... OP_EQUALVERIFY
| | ac ..................................... OP_CHECKSIG

00000000 ................................... locktime: 0 (a block height)

Updating A Bloom Filter

Clients will often want to track inputs that spend outputs (outpoints) relevant to their wallet, so the filterload field nFlags can be set to allow the filtering node to update the filter when a match is found. When the filtering node sees a pubkey script that pays a pubkey, address, or other data element matching the filter, the filtering node immediately updates the filter with the outpoint corresponding to that pubkey script.

If an input later spends that outpoint, the filter will match it, allowing the filtering node to tell the client that one of its transaction outputs has been spent.

The nFlags field has three allowed values:

Value	Name	Description
0	BLOOM_UPDATE_NONE	The filtering node should not update the filter.
1	BLOOM_UPDATE_ALL	If the filter matches any data element in a pubkey script, the corresponding outpoint is added to the filter.
2	BLOOM_UPDATE_P2PUBKEY_ONLY	If the filter matches any data element in a pubkey script and that script is either a P2PKH or non-P2SH pay-to-multisig script, the corresponding outpoint is added to the filter.

In addition, because the filter size stays the same even though additional elements are being added to it, the false positive rate increases. Each false positive can result in another element being added to the filter, creating a feedback loop that can (after a certain point) make the filter useless. For this reason, clients using automatic filter updates need to monitor the actual false positive rate and send a new filter when the rate gets too high.

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GetAddr

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The getaddr message requests an addr message from the receiving node, preferably one with lots of IP addresses of other receiving nodes. The transmitting node can use those IP addresses to quickly update its database of available nodes rather than waiting for unsolicited addr messages to arrive over time.

There is no payload in a getaddr message. See the [message header section][section message header] for an example of a message without a payload.

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GetSporks

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The getsporks message requests spork messages from the receiving node.

There is no payload in a getsporks message. See the [message header section][section message header] for an example of a message without a payload.

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Ping

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The ping message helps confirm that the receiving peer is still connected. If a TCP/IP error is encountered when sending the ping message (such as a connection timeout), the transmitting node can assume that the receiving node is disconnected. The response to a ping message is the pong message.

Before protocol version 60000, the ping message had no payload. As of protocol version 60001 and all later versions, the message includes a single field, the nonce.

Bytes	Name	Data Type	Description
8	nonce	uint64_t	Added in protocol version 60001 as described by BIP31. Random nonce assigned to this ping message. The responding pong message will include this nonce to identify the ping message to which it is replying.

The annotated hexdump below shows a ping message. (The message header has been omitted.)

{% highlight text %} 0094102111e2af4d ... Nonce {% endhighlight %}

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Pong

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Added in protocol version 60001 as described by BIP31.

The pong message replies to a ping message, proving to the pinging node that the ponging node is still alive. Dash Core will, by default, disconnect from any clients which have not responded to a ping message within 20 minutes.

To allow nodes to keep track of latency, the pong message sends back the same nonce received in the ping message it is replying to.

The format of the pong message is identical to the ping message; only the message header differs.

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Reject

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Added in protocol version 70002 as described by BIP61.

The reject message informs the receiving node that one of its previous messages has been rejected.

Bytes	Name	Data Type	Description
Varies	message bytes	compactSize uint	The number of bytes in the following message field.
Varies	message	string	The type of message rejected as ASCII text without null padding. For example: "tx", "block", or "version".
1	code	char	The reject message code. See the table below.
Varies	reason bytes	compactSize uint	The number of bytes in the following reason field. May be 0x00 if a text reason isn't provided.
Varies	reason	string	The reason for the rejection in ASCII text. This should not be displayed to the user; it is only for debugging purposes.
Varies	extra data	varies	Optional additional data provided with the rejection. For example, most rejections of tx messages or block messages include the hash of the rejected transaction or block header. See the code table below.

The following table lists message reject codes. Codes are tied to the type of message they reply to; for example there is a 0x10 reject code for transactions and a 0x10 reject code for blocks.

Code	In Reply To	Extra Bytes	Extra Type	Description
0x01	any message	0	N/A	Message could not be decoded. Be careful of reject message feedback loops where two peers each don't understand each other's reject messages and so keep sending them back and forth forever.
0x10	block message	32	char[32]	Block is invalid for some reason (invalid proof-of-work, invalid signature, etc). Extra data may include the rejected block's header hash.
0x10	tx message	32	char[32]	Transaction is invalid for some reason (invalid signature, output value greater than input, etc.). Extra data may include the rejected transaction's TXID.
0x10	ix message	32	char[32]	InstantSend transaction is invalid for some reason (invalid tx lock request, conflicting tx lock request, etc.). Extra data may include the rejected transaction's TXID.
0x11	block message	32	char[32]	The block uses a version that is no longer supported. Extra data may include the rejected block's header hash.
0x11	version message	0	N/A	Connecting node is using a protocol version that the rejecting node considers obsolete and unsupported.
0x11	dsa message	0	N/A	Connecting node is using a PrivateSend protocol version that the rejecting node considers obsolete and unsupported.
0x11	dsi message	0	N/A	Connecting node is using a PrivateSend protocol version that the rejecting node considers obsolete and unsupported.
0x11	dsc message	0	N/A	Connecting node is using a PrivateSend protocol version that the rejecting node considers obsolete and unsupported.
0x11	dsf message	0	N/A	Connecting node is using a PrivateSend protocol version that the rejecting node considers obsolete and unsupported.
0x11	dsq message	0	N/A	Connecting node is using a PrivateSend protocol version that the rejecting node considers obsolete and unsupported.
0x11	dssu message	0	N/A	Connecting node is using a PrivateSend protocol version that the rejecting node considers obsolete and unsupported.
0x11	govsync message	0	N/A	Connecting node is using a governance protocol version that the rejecting node considers obsolete and unsupported.
0x11	govobj message	0	N/A	Connecting node is using a governance protocol version that the rejecting node considers obsolete and unsupported.
0x11	govobjvote message	0	N/A	Connecting node is using a governance protocol version that the rejecting node considers obsolete and unsupported.
0x11	mnget message	0	N/A	Connecting node is using a masternode payment protocol version that the rejecting node considers obsolete and unsupported.
0x11	mnw message	0	N/A	Connecting node is using a masternode payment protocol version that the rejecting node considers obsolete and unsupported.
0x11	txlvote message	0	N/A	Connecting node is using an InstantSend protocol version that the rejecting node considers obsolete and unsupported.
0x12	tx message	32	char[32]	Duplicate input spend (double spend): the rejected transaction spends the same input as a previously-received transaction. Extra data may include the rejected transaction's TXID.
0x12	version message	0	N/A	More than one version message received in this connection.
0x40	tx message	32	char[32]	The transaction will not be mined or relayed because the rejecting node considers it non-standard---a transaction type or version unknown by the server. Extra data may include the rejected transaction's TXID.
0x41	tx message	32	char[32]	One or more output amounts are below the dust threshold. Extra data may include the rejected transaction's TXID.
0x42	tx message		char[32]	The transaction did not have a large enough fee or priority to be relayed or mined. Extra data may include the rejected transaction's TXID.
0x43	block message	32	char[32]	The block belongs to a block chain which is not the same block chain as provided by a compiled-in checkpoint. Extra data may include the rejected block's header hash.

Reject Codes

Code	Description
0x01	Malformed
0x10	Invalid
0x11	Obsolete
0x12	Duplicate
0x40	Non-standard
0x41	Dust
0x42	Insufficient fee
0x43	Checkpoint

The annotated hexdump below shows a reject message. (The message header has been omitted.)

{% highlight text %} 02 ................................. Number of bytes in message: 2 7478 ............................... Type of message rejected: tx 12 ................................. Reject code: 0x12 (duplicate) 15 ................................. Number of bytes in reason: 21 6261642d74786e732d696e707574732d 7370656e74 ......................... Reason: bad-txns-inputs-spent 394715fcab51093be7bfca5a31005972 947baf86a31017939575fb2354222821 ... TXID {% endhighlight %}

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SendCmpct

{% include helpers/subhead-links.md %}

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The sendcmpct message tells the receiving peer whether or not to announce new blocks using a cmpctblock message. It also sends the compact block protocol version it supports.

Bytes	Name	Data Type	Description
1	announce	bool	0 - Announce blocks via headers message or inv message 1 - Announce blocks via cmpctblock message
8	version	uint64_t	The compact block protocol version number

The annotated hexdump below shows a sendcmpct message. (The message header has been omitted.)

{% highlight text %} 01 ................................. Block announce type: Compact Blocks 0100000000000000 ................... Compact block version: 1 {% endhighlight %}

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SendHeaders

{% include helpers/subhead-links.md %}

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The sendheaders message tells the receiving peer to send new block announcements using a headers message rather than an inv message.

There is no payload in a sendheaders message. See the [message header section][section message header] for an example of a message without a payload.

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Spork

{% include helpers/subhead-links.md %}

{% autocrossref %} Sporks are a mechanism by which updated code is released to the network, but not immediately made active (or “enforced”). Enforcement of the updated code can be activated remotely. Should problems arise, the code can be deactivated in the same manner, without the need for a network-wide rollback or client update.

A spork message may be sent in response to a getsporks message.

The spork message tells the receiving peer the status of the spork defined by the SporkID field. Upon receiving a spork message, the client must verify the signature before accepting the spork message as valid.

Bytes	Name	Data type	Required	Description
4	nSporkID	int	Required	ID assigned in spork.h
8	nValue	int64_t	Required	Value assigned to spork
8	nTimeSigned	int64_t	Required	Time the spork value was signed
66	vchSig	char[]	Required	Length (1 byte) + Signature (65 bytes)

Sporks (per [src/spork.h][spork.h])

Spork ID	Number	Name	Description
10001	2	INSTANTSEND_ENABLED	Turns on and off InstantSend network wide
10002	3	INSTANTSEND_BLOCK_FILTERING	Turns on and off InstantSend block filtering
10004	5	INSTANTSEND_MAX_VALUE	Controls the max value for an InstantSend transaction (currently 2000 dash)
10005	6	NEW_SIGS	Turns on and off new signature format for Dash-specific messages
10007	8	MASTERNODE_PAYMENT_ENFORCEMENT	Requires masternodes to be paid by miners when blocks are processed
10008	9	SUPERBLOCKS_ENABLED	Superblocks are enabled (10% of the block reward allocated to fund the dash treasury for funding approved proposals)
10009	10	MASTERNODE_PAY_UPDATED_NODES	Only current protocol version masternode's will be paid (not older nodes)
10011	12	RECONSIDER_BLOCKS	Forces reindex of a specified number of blocks to recover from unintentional network forks
10013	14	REQUIRE_SENTINEL_FLAG	Only masternode's running sentinel will be paid
		Removed Sporks
10012	13	OLD_SUPERBLOCK_FLAG	Removed in Dash Core 0.12.3. No network function since block 614820

To verify vchSig, compare the hard-coded spork public key (strSporkPubKey from [src/chainparams.cpp][spork pubkey]) with the public key recovered from the spork message's hash and vchSig value (implementation details for Dash Core can be found in CPubKey::RecoverCompact). The hash is a double SHA-256 hash of:

• The spork magic message ("DarkCoin Signed Message:\n")
• nSporkID + nValue + nTimeSigned

Network	Spork Pubkey (wrapped)
Mainnet	04549ac134f694c0243f503e8c8a9a986f5de6610049c40b07816809b0d1 d06a21b07be27b9bb555931773f62ba6cf35a25fd52f694d4e1106ccd237 a7bb899fdd
Testnet3	046f78dcf911fbd61910136f7f0f8d90578f68d0b3ac973b5040fb7afb50 1b5939f39b108b0569dca71488f5bbf498d92e4d1194f6f941307ffd95f7 5e76869f0e
RegTest	Undefined
Devnets	046f78dcf911fbd61910136f7f0f8d90578f68d0b3ac973b5040fb7afb50 1b5939f39b108b0569dca71488f5bbf498d92e4d1194f6f941307ffd95f7 5e76869f0e

The following annotated hexdump shows a spork message.

{% highlight text %} 11270000 .................................... Spork ID: Spork 2 InstantSend enabled (10001) 0000000000000000 ............................ Value (0) 2478da5900000000 ............................ Epoch time: 2017-10-08 19:10:28 UTC (1507489828)

41 .......................................... Signature length: 65

1b6762d3e70890b5cfaed5d1fd72121c d32020c827a89f8128a00acd210f4ea4 1b36c26c3767f8a24f48663e189865ed 403ed1e850cdb4207cdd466419d9d183 45 .......................................... Masternode Signature {% endhighlight %}

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VerAck

{% include helpers/subhead-links.md %}

{% autocrossref %}

The verack message acknowledges a previously-received version message, informing the connecting node that it can begin to send other messages. The verack message has no payload; for an example of a message with no payload, see the [message headers section][section message header].

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Version

{% include helpers/subhead-links.md %}

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The version message provides information about the transmitting node to the receiving node at the beginning of a connection. Until both peers have exchanged version messages, no other messages will be accepted.

If a version message is accepted, the receiving node should send a verack message---but no node should send a verack message before initializing its half of the connection by first sending a version message.

Bytes	Name	Data Type	Required/Optional	Description
4	version	int32_t	Required	The highest protocol version understood by the transmitting node. See the [protocol version section][section protocol versions].
8	services	uint64_t	Required	The services supported by the transmitting node encoded as a bitfield. See the list of service codes below.
8	timestamp	int64_t	Required	The current Unix epoch time according to the transmitting node's clock. Because nodes will reject blocks with timestamps more than two hours in the future, this field can help other nodes to determine that their clock is wrong.
8	addr_recv services	uint64_t	Required	Added in protocol version 106. The services supported by the receiving node as perceived by the transmitting node. Same format as the 'services' field above. Dash Core will attempt to provide accurate information.
16	addr_recv IP address	char	Required	Added in protocol version 106. The IPv6 address of the receiving node as perceived by the transmitting node in big endian byte order. IPv4 addresses can be provided as [IPv4-mapped IPv6 addresses][]. Dash Core will attempt to provide accurate information.
2	addr_recv port	uint16_t	Required	Added in protocol version 106. The port number of the receiving node as perceived by the transmitting node in big endian byte order.
8	addr_trans services	uint64_t	Required	The services supported by the transmitting node. Should be identical to the 'services' field above.
16	addr_trans IP address	char	Required	The IPv6 address of the transmitting node in big endian byte order. IPv4 addresses can be provided as [IPv4-mapped IPv6 addresses][]. Set to ::ffff:127.0.0.1 if unknown.
2	addr_trans port	uint16_t	Required	The port number of the transmitting node in big endian byte order.
8	nonce	uint64_t	Required	A random nonce which can help a node detect a connection to itself. If the nonce is 0, the nonce field is ignored. If the nonce is anything else, a node should terminate the connection on receipt of a version message with a nonce it previously sent.
Varies	user_agent bytes	compactSize uint	Required	Number of bytes in following user_agent field. If 0x00, no user agent field is sent.
Varies	user_agent	string	Required if user_agent bytes > 0	Renamed in protocol version 60000. User agent as defined by BIP14. Previously called subVer. Dash Core limits the length to 256 characters.
4	start_height	int32_t	Required	The height of the transmitting node's best block chain or, in the case of an SPV client, best block header chain.
1	relay	bool	Optional	Added in protocol version 70001 as described by BIP37. Transaction relay flag. If 0x00, no inv messages or tx messages announcing new transactions should be sent to this client until it sends a filterload message or filterclear message. If the relay field is not present or is set to 0x01, this node wants inv messages and tx messages announcing new transactions.

The following service identifiers have been assigned.

Value	Name	Description
0x00	Unnamed	This node is not a full node. It may not be able to provide any data except for the transactions it originates.
0x01	NODE_NETWORK	This is a full node and can be asked for full blocks. It should implement all protocol features available in its self-reported protocol version.
0x02	NODE_GETUTXO	This node is capable of responding to the getutxo protocol request. Dash Core does not support this service.
0x04	NODE_BLOOM	This node is capable and willing to handle bloom-filtered connections. Dash Core nodes used to support this by default, without advertising this bit, but no longer do as of protocol version 70201 (= NO_BLOOM_VERSION)

The following annotated hexdump shows a version message. (The message header has been omitted and the actual IP addresses have been replaced with [RFC5737][] reserved IP addresses.)

{% highlight text %} 3e120100 .................................... Protocol version: 70206 0500000000000000 ............................ Services: NODE_NETWORK (1) + NODE_BLOOM (4) bc8f5e5400000000 ............................ Epoch time: 1415483324

0100000000000000 ............................ Receiving node's services 00000000000000000000ffffc61b6409 ............ Receiving node's IPv6 address 270f ........................................ Receiving node's port number

0500000000000000 ............................ Transmitting node's services 00000000000000000000ffffcb0071c0 ............ Transmitting node's IPv6 address 270f ........................................ Transmitting node's port number

128035cbc97953f8 ............................ Nonce

14 .......................................... Bytes in user agent string: 20 2f4461736820436f72653a302e31322e312e352f..... User agent: /Satoshi:0.9.2.1/

851f0b00 .................................... Start height: 728965 01 .......................................... Relay flag: true {% endhighlight %}

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InstantSend Messages

{% include helpers/subhead-links.md %}

{% autocrossref %}

The following network messages all help control the InstantSend feature of Dash. InstantSend uses the masternode network to lock transaction inputs and enable secure, instantaneous transactions. For additional details, refer to the Developer Guide InstantSend section.

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ix

{% include helpers/subhead-links.md %}

{% autocrossref %}

The ix message (transaction lock request) has the same structure as the tx message. The masternode network responds with txlvote messages if the transaction inputs can be locked.

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txlvote

{% include helpers/subhead-links.md %}

{% autocrossref %}

The txlvote message ([transaction lock vote][msg_txlock_vote]) is sent by masternodes to indicate approval of a transaction lock request ix message.

Bytes	Name	Data type	Required	Description
32	txHash	uint256	Required	TXID of the transaction to lock
36	outPoint	outpoint	Required	The unspent outpoint to lock in this transaction
36	outpointMasternode	outpoint	Required	The outpoint of the masternode which is signing the vote
66*	vchMasternodeSignature	char[]	Required	66 bytes in most cases. Length (1 byte) + Signature (65 bytes)

The following annotated hexdump shows a txlvote message. (The message header has been omitted.)

{% highlight text %} 3c121fb4a12b2f715e2f70a9fa282115 be197dde14073959fb2a2b8e95a7418f ..... TXID

Outpoint to lock | bb607995757c6a6efd6429215dcb3688 | b252d34d835c81fed310fd905f487020 ... Outpoint TXID | 01000000 ........................... Outpoint index number: 1

Masternode Outpoint | de9029c7e9b7eb7cd11f27ba670b2349 | 0c3f0717b86ed949c316874589405cd2 ... Outpoint TXID | 00000000 ........................... Outpoint index number: 0

41 ................................... Signature length: 65

1ccc39ffb9c62111a8c82823d3ce61d2 380db4e8f76ec238d568908f37558a90 4e79566a53663de12ec2be1183c87d61 250e8ebd57be171be1d4b5e89b69c263 88 ................................... Masternode Signature {% endhighlight %}

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PrivateSend Messages

{% include helpers/subhead-links.md %}

{% autocrossref %}

The following network messages all help control the PrivateSend (formerly DarkSend) coin mixing features built in to Dash and facilitated by the masternode network.

Since the messages are all related to a single process, this diagram shows them sequentially numbered. The dssu message (not shown) is sent by the masternode in conjunction with some responses. For additional details, refer to the Developer Guide PrivateSend section.

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dsa

{% include helpers/subhead-links.md %}

{% autocrossref %}

The dsa message allows a node to join a mixing pool. A collateral fee is required and may be forfeited if the client acts maliciously. The message operates in two ways:

1. When sent to a masternode without a current mixing queue, it initiates the start of a new mixing queue

2. When sent to a masternode with a current mixing queue, it attempts to join the existing queue

Dash Core starts a new queue ~33% of the time and attempts to join an existing queue the remainder of the time.

Bytes	Name	Data type	Required	Description
4	nDenom	int	Required	Denomination that will be exclusively used when submitting inputs into the pool
216+	txCollateral	tx message	Required	Collateral TX that will be charged if this client acts maliciously

The following annotated hexdump shows a dsa message. (The message header has been omitted.)

{% highlight text %} 02000000 ................................... Denomination: 1 Dash (2)

Collateral Transaction | Previous Output | | | | 010000000183bd1980c71c38f035db9b | | 14d7f934f7d595181b3436e362899026 ....... Outpoint TXID | | 19f3f7d3 ............................... Outpoint index number: 3556242201 | | 83 ....................................... Bytes in sig. script: 131 | | 000000006b483045022100f4d8fa0ae4132235fe | cd540a62715ccfb1c9a97f8698d066656e30bb1e | 1e06b90220301b4cc93f38950a69396ed89dfcc0 | 8e72ec8e6e7169463592a0bf504946d98b812102 | fa4b9c0f9e76e06d57c75cab9c8368a62a1ce8db | 6eb0c25c3e0719ddd9ab549cffffffff01e09304 | 00000000001976a914f895 ................... Secp256k1 signature: None | | 6a4eb0e5 ................................. Sequence number: 3853536874 {% endhighlight %}

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dsc

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{% autocrossref %}

The dsc message indicates a PrivateSend mixing session is complete.

Bytes	Name	Data type	Required	Description
4	nSessionID	int	Required	ID of the mixing session
4	nMessageID	int	Required	ID of the message describing the result of the mixing session

Reference the Message IDs table under the dssu message for descriptions of the Message ID values.

The following annotated hexdump shows a dsc message. (The message header has been omitted.)

{% highlight text %} d9070700 ............................. Session ID: 791686 14000000 ............................. Message ID: MSG_SUCCESS (20) {% endhighlight %}

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dsf

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The dsf message is sent by the masternode as the final mixing transaction in a PrivateSend mixing session. The masternode expects nodes in the mixing session to respond with a dss message.

Bytes	Name	Data type	Required	Description
4	nSessionID	int	Required	ID of the mixing session
#	txFinal	tx message	Required	Final mixing transaction with unsigned inputs

The following annotated hexdump shows a dsf message. (The message header has been omitted.) Transaction inputs/outputs are only shown for a single node (compare with the dsi message and dss message hexdumps).

{% highlight text %} 86140c00 ............................. Session ID: 791686

Transaction Message | 01000000 ................................. Version: 1 | | 0f ......................................... Number of inputs: 15 | | [...] ...................................... 5 transaction inputs omitted | | Transaction input #6 | | | | 36bdc3796c5630225f2c86c946e2221a | | 9958378f5d08da380895c2656730b5c0 ......... Outpoint TXID | | 02000000 ................................. Outpoint index number: 0 | | | | 00 ....................................... Bytes in sig. script: 0 | | .......................................... Secp256k1 signature: None | | | | ffffffff ................................. Sequence number: UINT32_MAX | | Transaction input #7 | | | | 36bdc3796c5630225f2c86c946e2221a | | 9958378f5d08da380895c2656730b5c0 ......... Outpoint TXID | | 0f000000 ................................. Outpoint index number: 15 | | | | 00 ....................................... Bytes in sig. script: 0 | | .......................................... Secp256k1 signature: None | | | | ffffffff ................................. Sequence number: UINT32_MAX | | Transaction input #8 | | | | 36bdc3796c5630225f2c86c946e2221a | | 9958378f5d08da380895c2656730b5c0 ......... Outpoint TXID | | 0d000000 ................................. Outpoint index number: 13 | | | | 00 ....................................... Bytes in sig. script: 0 | | .......................................... Secp256k1 signature: None | | | | ffffffff ................................. Sequence number: UINT32_MAX | | | [...] ...................................... 7 more transaction inputs omitted | | | 0f ......................................... Number of outputs: 15 | | Transaction output #1 | | e8e4f50500000000 ......................... Duffs (1.00001 Dash) | | | | 19 ....................................... Bytes in pubkey script: 25 | | | 76 ..................................... OP_DUP | | | a9 ..................................... OP_HASH160 | | | 14 ..................................... Push 20 bytes as data | | | | 14826d7ba05cf76588a5503c03951dc9 | | | | 14c91b6c ............................. PubKey hash | | | 88 ..................................... OP_EQUALVERIFY | | | ac ..................................... OP_CHECKSIG | | | [...] ...................................... 3 transaction outputs omitted | | | Transaction output #5 | | e8e4f50500000000 ......................... 100,001,000 Duffs (1.0001 Dash) | | | | 19 ....................................... Bytes in pubkey script: 25 | | | 76 ..................................... OP_DUP | | | a9 ..................................... OP_HASH160 | | | 14 ..................................... Push 20 bytes as data | | | | 426614716e94812d483bca32374f6ac8 | | | | cd121b0d ............................. PubKey hash | | | 88 ..................................... OP_EQUALVERIFY | | | ac ..................................... OP_CHECKSIG | | | [...] ...................................... 9 transaction outputs omitted | | | Transaction output #15 | | e8e4f50500000000 ......................... 100,001,000 Duffs (1.0001 Dash) | | | | 19 ....................................... Bytes in pubkey script: 25 | | | 76 ..................................... OP_DUP | | | a9 ..................................... OP_HASH160 | | | 14 ..................................... Push 20 bytes as data | | | | f01197177de2358928196a543b2bbd97 | | | | 3c2ab002 ............................. PubKey hash | | | 88 ..................................... OP_EQUALVERIFY | | | ac ..................................... OP_CHECKSIG | | 00000000 ................................... locktime: 0 (a block height) {% endhighlight %}

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dsi

{% include helpers/subhead-links.md %}

{% autocrossref %}

The dsi message replies to a dsq message that has the Ready field set to 0x01. The dsi message contains user inputs for mixing along with the outputs and a collateral. Once the masternode receives dsi messages from all members of the pool, it responds with a dsf message.

Bytes	Name	Data type	Required	Description
?	vecTxDSIn	CTxDSIn[]	Required	Vector of users inputs (CTxDSIn serialization is equal to CTxIn serialization)
216+	txCollateral	tx message	Required	Collateral transaction which is used to prevent misbehavior and also to charge fees randomly
?	vecTxDSOut	CTxDSOut[]	Required	Vector of user outputs (CTxDSOut serialization is equal to CTxOut serialization)

The following annotated hexdump shows a dsi message. (The message header has been omitted.)

{% highlight text %} User inputs | 03 ......................................... Number of inputs: 3 | | Transaction input #1 | | | | 36bdc3796c5630225f2c86c946e2221a | | 9958378f5d08da380895c2656730b5c0 ......... Outpoint TXID | | 02000000 ................................. Outpoint index number: 2 | | | | 00 ....................................... Bytes in sig. script: 0 | | .......................................... Secp256k1 signature: None | | | | ffffffff ................................. Sequence number: UINT32_MAX | | Transaction input #2 | | | | 36bdc3796c5630225f2c86c946e2221a | | 9958378f5d08da380895c2656730b5c0 ......... Outpoint TXID | | 0f000000 ................................. Outpoint index number: 15 | | | | 00 ....................................... Bytes in sig. script: 0 | | .......................................... Secp256k1 signature: None | | | | ffffffff ................................. Sequence number: UINT32_MAX | | Transaction input #3 | | | | 36bdc3796c5630225f2c86c946e2221a | | 9958378f5d08da380895c2656730b5c0 ......... Outpoint TXID | | 0d000000 ................................. Outpoint index number: 13 | | | | 00 ....................................... Bytes in sig. script: 0 | | .......................................... Secp256k1 signature: None | | | | ffffffff ................................. Sequence number: UINT32_MAX

Collateral Transaction | 01000000 ................................... Version: 1 | | 01 ......................................... Number of inputs: 1 | | Previous Output | | | | 83bd1980c71c38f035db9b14d7f934f7 | | d595181b3436e36289902619f3f7d383 ......... Outpoint TXID | | 00000000 ................................. Outpoint index number: 0 | | | | 6b ....................................... Bytes in sig. script: 107 | | | | 483045022100f4d8fa0ae4132235fecd540a | | 62715ccfb1c9a97f8698d066656e30bb1e1e | | 06b90220301b4cc93f38950a69396ed89dfc | | c08e72ec8e6e7169463592a0bf504946d98b | | 812102fa4b9c0f9e76e06d57c75cab9c8368 | | a62a1ce8db6eb0c25c3e0719ddd9ab549c ....... Secp256k1 signature | | | | ffffffff ................................. Sequence number: UINT32_MAX | | 01 ......................................... Number of outputs: 1 | | | e093040000000000 ......................... 300,000 Duffs (0.003 Dash) | | | | 19 ....................................... Bytes in pubkey script: 25 | | | 76 ..................................... OP_DUP | | | a9 ..................................... OP_HASH160 | | | 14 ..................................... Push 20 bytes as data | | | | f8956a4eb0e53b05ee6b30edfd2770b5 | | | | 26c1f1bb ............................. PubKey hash | | | 88 ..................................... OP_EQUALVERIFY | | | ac ..................................... OP_CHECKSIG | | 00000000 ................................... locktime: 0 (a block height)

User outputs | 03 ......................................... Number of outputs: 3 | | Transaction output #1 | | e8e4f50500000000 ......................... 100,001,000 Duffs (1.0001 Dash) | | | | 19 ....................................... Bytes in pubkey script: 25 | | | 76 ..................................... OP_DUP | | | a9 ..................................... OP_HASH160 | | | 14 ..................................... Push 20 bytes as data | | | | 14826d7ba05cf76588a5503c03951dc9 | | | | 14c91b6c ............................. PubKey hash | | | 88 ..................................... OP_EQUALVERIFY | | | ac ..................................... OP_CHECKSIG | | Transaction output #2 | | e8e4f50500000000 ......................... 100,001,000 Duffs (1.0001 Dash) | | | | 19 ....................................... Bytes in pubkey script: 25 | | | 76 ..................................... OP_DUP | | | a9 ..................................... OP_HASH160 | | | 14 ..................................... Push 20 bytes as data | | | | f01197177de2358928196a543b2bbd97 | | | | 3c2ab002 ............................. PubKey hash | | | 88 ..................................... OP_EQUALVERIFY | | | ac ..................................... OP_CHECKSIG | | Transaction output #3 | | e8e4f50500000000 ......................... 100,001,000 Duffs (1.0001 Dash) | | | | 19 ....................................... Bytes in pubkey script: 25 | | | 76 ..................................... OP_DUP | | | a9 ..................................... OP_HASH160 | | | 14 ..................................... Push 20 bytes as data | | | | 426614716e94812d483bca32374f6ac8 | | | | cd121b0d ............................. PubKey hash | | | 88 ..................................... OP_EQUALVERIFY | | | ac ..................................... OP_CHECKSIG {% endhighlight %}

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dsq

{% include helpers/subhead-links.md %}

{% autocrossref %}

The dsq message provides nodes with mixing queue details and notifies them when to sign final mixing TX messages.

If the message indicates the queue is not ready, the node verifies the message is valid. It also verifies that the masternode is not flooding the network with dsq messages in an attempt to dominate the queuing process. It then relays the message to its connected peers.

If the message indicates the queue is ready, the node responds with a dsi message.

Bytes	Name	Data type	Required	Description
4	nDenom	int	Required	Denomination allowed in this mixing session
36	masternodeOutPoint	outPoint	Required	The unspent outpoint of the masternode (holding 1000 DASH) which is hosting this session
8	nTime	int64_t	Required	Time this dsq message was created
1	fReady	bool	Required	Indicates if the mixing pool is ready to be executed
66*	vchSig	char[]	Required	Signature of this message by masternode verifiable via pubKeyMasternode (Length (1 byte) + Signature (65 bytes))

Denominations (per [src/privatesend.cpp][privatesend denominations])

Value	Denomination
1	10 Dash
2	1 Dash
4	0.1 Dash
8	0.01 Dash

The following annotated hexdump shows a dsq message. (The message header has been omitted.)

{% highlight text %} 08000000 ............................. Denomination: 0.01 Dash (8)

Masternode Outpoint | aeed0e77c6db30a616507a37a129bc88 | 1811f08afc51dd485d5322f36c1f04c5 ... Outpoint TXID | 01000000 ........................... Outpoint index number: 1

1318a85900000000 ..................... Create Time: 2017-08-31 14:07:15 UTC

00 ................................... Ready: 0

41 ................................... Signature length: 65

1bd74386ea4e111197f1b4b4660c1415 13486745ca10ba0632426ed3a644d941 047e43c988680904d4a4fcf551d8813c ec12d47ae9b00e870db294cd66708ab7 dc ................................... Masternode Signature {% endhighlight %}

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dss

{% include helpers/subhead-links.md %}

{% autocrossref %}

The dss message replies to a dsf message sent by the masternode managing the mixing session. The dsf message provides the unsigned transaction inputs for all members of the mixing pool. Each node verifies that the final transaction matches what is expected. They then sign any transaction inputs belonging to them and then relay them to the masternode via this dss message.

Once the masternode receives and validates all dss messages, it issues a dsc message. If a node does not respond to a dsf message with signed transaction inputs, it may forfeit the collateral it provided. This is to minimize malicious behavior.

Bytes	Name	Data type	Required	Description
#	inputs	txIn[]	Required	Signed inputs for mixing session

The following annotated hexdump shows a dss message. (The message header has been omitted.) Note that these will be the same transaction inputs that were supplied (unsiged) in the dsi message.

{% highlight text %} User inputs | 03 ......................................... Number of inputs: 3 | | Transaction input #1 | | | | 36bdc3796c5630225f2c86c946e2221a | | 9958378f5d08da380895c2656730b5c0 ......... Outpoint TXID | | 02000000 ................................. Outpoint index number: 2 | | | | 6b ....................................... Bytes in sig. script: 107 | | 483045022100b3a861dca83463aabf5e4a14a286 | | 1b9c2e51e0dedd8a13552e118bf74eb4a68d0220 | | 4a91c416768d27e6bdcfa45d28129841dbcc728b | | f0bbec9701cfc4e743d23adf812102cc4876c9da | | 84417dec37924e0479205ce02529bb0ba88631d3 | | ccc9cfcdf00173 ........................... Secp256k1 signature | | | | ffffffff ................................. Sequence number: UINT32_MAX | | Transaction input #2 | | | | 36bdc3796c5630225f2c86c946e2221a | | 9958378f5d08da380895c2656730b5c0 ......... Outpoint TXID | | 0f000000 ................................. Outpoint index number: 15 | | | | 6a ....................................... Bytes in sig. script: 106 | | 4730440220268f3b7799ca4ec132e511a4756019 | | c56016f7771561dc0597d84e9b1fa9fc08022067 | | 5199b9b3f9a7eba69b7bbb4aa2a413d955762f9d | | 68be5a9c02c6772c8078fd812103258925f0dbbf | | 9d5aa20a675459fa2e86c9f9061dee82a00dca73 | | 9080f051d891 ............................. Secp256k1 signature | | | | ffffffff ................................. Sequence number: UINT32_MAX | | Transaction input #3 | | | | 36bdc3796c5630225f2c86c946e2221a | | 9958378f5d08da380895c2656730b5c0 ......... Outpoint TXID | | 0d000000 ................................. Outpoint index number: 13 | | | | 6a ....................................... Bytes in sig. script: 106 | | 4730440220404bb067e0c94a2bd75c6798c1af8c | | 95e8b92f5e437cff2bcb4660f24a34d06d02203a | | b707bd371a84a9e7bd1fbe3b0c939fd23e0a9165 | | de78809b9310372a4b3879812103a9a6c5204811 | | a8cab04b595ed622a1fed6efd3b2d888fadd0c97 | | 3737fcdf2bc7 ............................. Secp256k1 signature | | | | ffffffff ................................. Sequence number: UINT32_MAX {% endhighlight %}

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dssu

{% include helpers/subhead-links.md %}

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The dssu message provides a mixing pool status update.

Bytes	Name	Data type	Required	Description
4	nMsgSessionID	int	Required	Session ID
4	nMsgState	int	Required	Current state of mixing process
4	nMsgEntriesCount	int	Required	Number of entries in the mixing pool
4	nMsgStatusUpdate	int	Required	Update state and/or signal if entry was accepted or not
4	nMsgMessageID	int	Required	ID of the typical masternode reply message

Pool State

State	Description
0	POOL_STATE_IDLE
1	POOL_STATE_QUEUE
2	POOL_STATE_ACCEPTING_ENTRIES
3	POOL_STATE_SIGNING
4	POOL_STATE_ERROR
5	POOL_STATE_SUCCESS

Pool Status Update

Status	Description
0	STATUS_REJECTED
1	STATUS_ACCEPTED

Message IDs

Code	Description
0x00	ERR_ALREADY_HAVE
0x01	ERR_DENOM
0x02	ERR_ENTRIES_FULL
0x03	ERR_EXISTING_TX
0x04	ERR_FEES
0x05	ERR_INVALID_COLLATERAL
0x06	ERR_INVALID_INPUT
0x07	ERR_INVALID_SCRIPT
0x08	ERR_INVALID_TX
0x09	ERR_MAXIMUM
0x0A (10)	ERR_MN_LIST
0x0B (11)	ERR_MODE
0x0C (12)	ERR_NON_STANDARD_PUBKEY
0x0D (13)	ERR_NOT_A_MN (Not used)
0x0E (14)	ERR_QUEUE_FULL
0x0F (15)	ERR_RECENT
0x10 (16)	ERR_SESSION
0x11 (17)	ERR_MISSING_TX
0x12 (18)	ERR_VERSION
0x13 (19)	MSG_NOERR
0x14 (20)	MSG_SUCCESS
0x15 (21)	MSG_ENTRIES_ADDED

The following annotated hexdump shows a dssu message. (The message header has been omitted.)

{% highlight text %} 86140c00 ............................. Session ID: 791686 02000000 ............................. State: POOL_STATE_ACCEPTING_ENTRIES (2) 03000000 ............................. Entries: 3 01000000 ............................. Status Update: STATUS_ACCEPTED (1) 13000000 ............................. Message ID: MSG_NOERR (0x13) {% endhighlight %}

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dstx

{% include helpers/subhead-links.md %}

{% autocrossref %}

The dstx message allows masternodes to broadcast subsidized transactions without fees (to provide security in mixing).

Bytes	Name	Data type	Required	Description
#	tx	tx message	Required	The transaction
36	masternodeOutPoint	outPoint	Required	The unspent outpoint of the masternode (holding 1000 DASH) which is signing the message
66	vchSig	char[]	Required	Signature of this message by masternode verifiable via pubKeyMasternode (Length (1 byte) + Signature (65 bytes))
8	sigTime	int64_t	Require	Time this message was signed

The following annotated hexdump shows a dstx message. (The message header has been omitted.)

{% highlight text %} Transaction Message | 01000000 ................................. Version: 1 | | 0b ......................................... Number of inputs: 11 | | Transaction input #1 | | | | 0adb782b2170018eada54534be880e70 | | 74ed8307a566731119b1782362af43ad ......... Outpoint TXID | | 05000000 ................................. Outpoint index number: 5 | | | | 6a ....................................... Bytes in sig. script: 106 | | 47304402204ed56f525ae6df707f9cbe | | 55c78d82bbcc02daa1fb27b0bf54588a | | 446dcc804102200c4e03c4a2b9a90aef | | 9f01de7c28812a0e8b280e6c153b0bd8 | | 26d2ff660102e18121028c96903b2709 | | 7b331d55abd1f42d2ff6cc7c784ab839 | | 7c232b73a34a149a348e ..................... Secp256k1 signature | | | | ffffffff ................................. Sequence number: UINT32_MAX | | [...] ...................................... 10 more transaction inputs omitted | | | 0b ......................................... Number of outputs: 11 | | Transaction output #1 | | e8e4f50500000000 ......................... Duffs (1.00001000 Dash) | | | | 19 ....................................... Bytes in pubkey script: 25 | | | 76 ..................................... OP_DUP | | | a9 ..................................... OP_HASH160 | | | 14 ..................................... Push 20 bytes as data | | | | 0febbeaa8818b2c2f80fb8c98f90bdae | | | | 41fe5c26 ............................. PubKey hash | | | 88 ..................................... OP_EQUALVERIFY | | | ac ..................................... OP_CHECKSIG | | [...] ...................................... 10 more transaction outputs omitted | | | 00000000 ................................... locktime: 0 (a block height)

Masternode Unspent Outpoint | 387d522def2abfb9bdd15be899f074f3 | 49b414cef078ec642e1d14b42996b9fc ......... Outpoint TXID | 00000000 ................................. Outpoint index number: 0

1b6fb8f90f0df6e502bc10aab9604e49 2d14214e05331c9761c834d55c7536e3 3369e5909479ea88116aad7ea64587d9 59364326c97d7f249f7b9293e120a5b6 1c ................................... Masternode Signature

ece5a95900000000 ..................... Signature Timestamp {% endhighlight %}

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Masternode Messages

{% include helpers/subhead-links.md %}

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The following network messages enable the masternode features built in to Dash.

For additional details, refer to the Developer Guide Masternode Sync and Masternode Payment sections.

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dseg

{% include helpers/subhead-links.md %}

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The dseg message requests either the entire masternode list or a specific entry. To request the list of all masternodes, use an empty txIn (TXID of all zeros and an index of 0xFFFFFFFF). To request information about a specific masternode, use the unspent outpoint associated with that masternode.

The response to a dseg message is an mnb message inventory and an mnp message inventory for each requested masternode. Masternodes ignore this request if they are not fully synced.

Bytes	Name	Data type	Required	Description
36	masternodeOutPoint	outPoint	Required	Request options: All Entries - empty txIn Single Entry - Masternode's unspent outpoint which is holding 1000 DASH

{% highlight text %} Note: Dash Core only allows nodes to request the entire list every 3 hours. Additional requests sent prior to then may result in the node being banned. {% endhighlight %}

The following annotated hexdump shows a dseg message requesting all masternodes. (The message header has been omitted.)

{% highlight text %} Masternode Unspent Outpoint | 00000000000000000000000000000000 | 00000000000000000000000000000000 ......... Outpoint TXID | ffffffff ................................. Outpoint index number: 0 {% endhighlight %}

The following annotated hexdump shows a dseg message requesting a specific masternode. (The message header has been omitted.)

{% highlight text %} Masternode Unspent Outpoint | 7fe33a2901aa654598ae0af572d4fbec | ee97af2d0276f189d177dee5848ef3da ......... Outpoint TXID | 00000000 ................................. Outpoint index number: 0 {% endhighlight %}

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mnb

{% include helpers/subhead-links.md %}

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The mnb message is sent whenever a masternode comes online or a client is syncing. The masternode will send this message which describes the masternode entry and how to validate messages from it.

Bytes	Name	Data type	Required	Description
36	outPoint	outPoint	Required	The unspent outpoint of the masternode (holding 1000 DASH) which is signing the message
#	addr	CService	Required	IPv4 address of the masternode
33-65	pubKeyCollateralAddress	CPubKey	Required	CPubKey of the main 1000 DASH unspent outpoint. Length determined by if it is a compressed public key or not.
33-65	pubKeyMasternode	CPubKey	Required	CPubKey of the secondary signing key (For all messaging other than the announce message). Length determined by if it is a compressed public key or not.
66	sig	char[]	Required	Signature of this message verifiable via pubKeyMasternode (Length (1 byte) + Signature (65 bytes))
8	sigTime	int64_t	Required	Time which the signature was created
4	nProtocolVersion	int	Required	The protocol version of the masternode
#	lastPing	mnp message	Required	The last known ping of the masternode
8	nLastDsq	int64_t	Deprecated	Removed in Dash Core 0.12.3.0 The last time the masternode sent a dsq message (for mixing) (DEPRECATED)

The following annotated hexdump shows a mnb message. (The message header has been omitted and the actual IP address has been replaced with a RFC5737 reserved IP address.)

{% highlight text %} Masternode Unspent Outpoint | 3fbc7d4a8f68ba6ecb02a8db34d1f5b6 | 2dc105f0b5c3505243435cf815d02394 ......... Outpoint TXID | 01000000 ................................. Outpoint index number: 1

Masternode Address | 00000000000000000000ffffc0000233 ......... IP Address: ::ffff:192.0.2.51 | 270f ..................................... Port: 9999

Collateral Public Key | 21 ....................................... Key Size: 33 | 02 ....................................... Key Type: 2 - Compressed (even) | 02a47a6845936a4199e126d35399dd09 | 97c1aaf89a3fe70d474c53f29624a43a5b ....... Public Key

Masternode Public Key | 41 ....................................... Key Size: 65 | 04 ....................................... Key Type: 4 - Uncompressed | 04da252243305d604cab90480880af4a | b5cea3a934c91393452e9b7b4c97a87e | 198bc809916ac2c27436a1db9c28d0aa | bfefec4dc3c2193835fd9a56c31150c633 ....... Public Key

Message Signature | 41 ....................................... Bytes in signature: 65 | 1fb80f9ba8c110835e4a7dd4c8deccd7 | 89027663d00084d9a99ef579a9b5601f | 40727b27e91aab2897a078f63976ae25 | 3ff8f01e56862e953278f432530f6ee080 ....... Signature

4728ef5800000000 ........................... Sig. Timestamp: 2017-04-13 07:27:03 UTC

3e120100 ................................... Protocol Version: 70206

Masternode Ping Message | Masternode Unspent Outpoint | | 3fbc7d4a8f68ba6ecb02a8db34d1f5b6 | | 2dc105f0b5c3505243435cf815d02394 ........ Outpoint TXID | | 01000000 ................................ Outpoint index number: 1 | | 94fc0fad18b166c2fedf1a5dc0511372 | 26c353d57e086737ff05000000000000 ......... Chaintip block hash | | 66c1a95900000000 ......................... Sig. Timestamp: 2017-10-01 21:21:58 UTC | | Masternode Signature | | 41 ..................................... Bytes in signature: 65 | | 1b3017c49a03e2d77083f3c92a8c2e4c | | d815d068b6256498a719e3cb6a34f774 | | ec6434cfcbb7a5a51704350a05903287 | | eecc82e6b40ac2fcfa2df29ddaa6c4fc | | b8 ..................................... Masternode Signature {% endhighlight %}

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mnget

{% include helpers/subhead-links.md %}

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The mnget message requests masternode payment sync. The response to an mnget message is mnw message inventories. Masternodes ignore this request if they are not fully synced.

In protocol versions <=70208, the mnget message has a payload consisting of an integer value requesting a specific number of payment votes. In protocol versions

70208, the mnget message has no payload.

Bytes	Name	Data type	Required	Description
4	nMnCount	int	Deprecated	Deprecated in Dash Core 0.12.3 Number of masternode payment votes to request

{% highlight text %} Note: Dash Core limits how frequently a masternode payment sync can be requested. Frequent requests will result in the node being banned. {% endhighlight %}

The following annotated hexdump shows a pre-0.12.3 mnget message. (The message header has been omitted.)

{% highlight text %} a8170000 ................................... Count: 6056 {% endhighlight %}

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mnp

{% include helpers/subhead-links.md %}

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The mnp message is sent by masternodes every few minutes to ping the network with a message that propagates across the whole network. Dash Core currently uses a minimum masternode ping time of 10 minutes.

Bytes	Name	Data type	Required	Description
36	masternodeOutPoint	outPoint	Required	The unspent outpoint of the masternode (holding 1000 DASH) which is signing the message
32	blockHash	uint256	Required	Block hash from 12 blocks ago (current chaintip minus 12). This offset allows nodes to be slightly out of sync.
8	sigTime	int64_t	Required	Time which the signature was created
66*	vchSig	char[]	Required	Signature of this message by masternode - verifiable via pubKeyMasternode (66 bytes in most cases. Length (1 byte) + Signature (65 bytes))
1	fSentinelIsCurrent	bool	Required	True if last sentinel ping was current
4	nSentinelVersion	uint32_t	Required	The version of Sentinel running on the masternode which is signing the message
4	nDaemonVersion	uint32_t	Required	The version of dashd on the masternode which is signing the message (i.e. CLIENT_VERSION)

The following annotated hexdump shows a mnp message. (The message header has been omitted.)

{% highlight text %} Masternode Unspent Outpoint | 0bfa3616099771bb5f36181ff4060a9b | 9afe7b3e47d7f4327800f0f8ce586c6e ......... Outpoint TXID | 01000000 ................................. Outpoint index number: 1

a26a68ebb733192c1c40f9b42f872ac0 e23d4c360e20d5ab6608000000000000 ........... Chaintip block hash

1bbfa95900000000 ........................... Sig. Timestamp: 2017-10-01 20:12:11 UTC

Masternode Signature | 41 ....................................... Bytes in signature: 65 | 1c2b205bd6ba472d7a9495f049ef66dc | f844154846e25f2389385ba2d3e95cde | cf3ccf82bc26d94c6fdafcd7b965bb61 | db02d05483595196ea4d92b2e797612b | 79 ....................................... Masternode Signature {% endhighlight %}

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mnv

{% include helpers/subhead-links.md %}

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The mnv message is used by masternodes to verify each other. Several mnv messages are exchanged in the process. This results in the IP address of masternode 1 being validated as of the provided block height.

Bytes	Name	Data type	Required	Description
36	masternodeOutPoint1	outPoint	Required	The unspent outpoint which is holding 1000 DASH for masternode 1
36	masternodeOutPoint2	outPoint	Required	The unspent outpoint which is holding 1000 DASH for masternode 2
#	addr	CService	Required	IPv4 address and port of masternode 1
4	nonce	int	Required	Random nonce
4	nBlockHeight	int	Required	Block height
66	vchSig1	char[]	Required* Added in Step 2	Signature of this message by masternode 1 - verifiable via pubKeyMasternode (Length (1 byte) + Signature (65 bytes))
66	vchSig2	char[]	Required* Added in Step 3	Signature of this message by masternode 2 - verifiable via pubKeyMasternode (Length (1 byte) + Signature (65 bytes))

Initially, vin1, vin2, vchSig1 and vchSig2 are empty. They are updated as the exchange of messages between the masternodes occurs as detailed in the table below.

Masternode Verify Data Flow

| Step | MN 2 (Verifier) | Direction | MN 1 (Being verified) | Description | | | Verification request | | | mnv message with no signatures | | 1 | mnv message | → | | Contains addr, nonce, and nBlockHeight.
Sent by SendVerifyRequest(). | 2 | | ← | mnv message | Add vchSig1 (signature of the IP address + nonce + hash of the requested block).
Sent by SendVerifyReply(). | 3 | mnv message | → | | Verify vchSig1

Add masternodeOutPoint1, masternodeOutPoint2, and vchSig2 (signature of the IP address + nonce + hash of the requested block + masternodeOutPoint1 + masternodeOutPoint2) and relay message to peers if valid.
Sent by ProcessVerifyReply().

Nodes receiving a relayed mnv message (one in which masternodeOutPoint1, masternodeOutPoint2, vchSig1 and vchSig2 are already present) use it to update the PoSe ban score. If the ban score reaches MASTERNODE_POSE_BAN_MAX_SCORE (5), the masternode will be considered malicious and banned. If the received message is valid, nodes receiving it will relay it on to their connected peers.

{% highlight text %} Important Notes:

• Dash Core limits how frequently a masternode verify request can be requested. Frequent requests will result in the node being banned.

• Only masternodes in the top MAX_POSE_RANK (10) can send an mnv request (to no more than MAX_POSE_CONNECTIONS (10)).

{% endhighlight %}

The following annotated hexdump shows a mnv message. This is an example of the initial request (Step 1) so it does not contain any signatures. (The message header has been omitted.)

{% highlight text %} Masternode 1 Unspent Outpoint (empty) | 00000000000000000000000000000000 | 00000000000000000000000000000000 ......... Outpoint TXID | ffffffff ................................. Outpoint index number: 0

Masternode 2 Unspent Outpoint (empty) | 00000000000000000000000000000000 | 00000000000000000000000000000000 ......... Outpoint TXID | ffffffff ................................. Outpoint index number: 0

00000000000000000000ffff2d20ed4c ........... IP Address: ::ffff:45.32.237.76 4e1f ....................................... Port: 19999 9d090000 ................................... Nonce: 2641 ed5c0000 ................................... Block height: 23789

Masternode 1 Signature | 00 ....................................... Bytes in signature: 0 | .......................................... Signature: Empty

Masternode 2 Signature | 00 ....................................... Bytes in signature: 0 | .......................................... Signature: Empty {% endhighlight %}

The following annotated hexdump shows a mnv message. This is an example of the initial response (Step 2) so it only contains the signature of masternode 1 (the masternode being verified). (The message header has been omitted.)

{% highlight text %} Masternode 1 Unspent Outpoint (empty) | 00000000000000000000000000000000 | 00000000000000000000000000000000 ......... Outpoint TXID | ffffffff ................................. Outpoint index number: 0

Masternode 2 Unspent Outpoint (empty) | 00000000000000000000000000000000 | 00000000000000000000000000000000 ......... Outpoint TXID | ffffffff ................................. Outpoint index number: 0

00000000000000000000ffff2d20ed4c ........... IP Address: ::ffff:45.32.237.76 4e1f ....................................... Port: 19999 9d090000 ................................... Nonce: 2641 ed5c0000 ................................... Block height: 23789

Masternode 1 Signature | 41 ....................................... Bytes in signature: 65 | 1bf5bd6e6eda0cd32aafb826c4066fa5 | 4a53baa6f4211528e51716054b4df981 | d97a77e633947bbbfafd6882324b76a0 | 90c6e65c16ca1222db48f8558537c062 | f6 ....................................... Signature

Masternode 2 Signature | 00 ....................................... Bytes in signature: 0 | .......................................... Signature: Empty {% endhighlight %} {% endautocrossref %}

mnw

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The mnw message is used to pick the next winning masternode. When a new block is found on the network, a masternode quorum will be determined and those 10 selected masternodes will issue the masternode payment vote message.

Bytes	Name	Data type	Required	Description
36	masternodeOutPoint	outPoint	Required	The unspent outpoint of the masternode (holding 1000 DASH) which is signing the message
4	nBlockHeight	int	Required	The blockheight which the payee should be paid
?	payeeAddress	CScript	Required	The address receiving payment
66*	vchSig	char[]	Required	Signature of the masternode which is signing the message (66 bytes in most cases. Length (1 byte) + Signature (65 bytes))

The following annotated hexdump shows a mnw message. (The message header has been omitted.)

{% highlight text %} Masternode Unspent Outpoint | 0c1b5c5846792b25b05eeea9586d8c34 | ecb996c566bedb4ecf6a68fe8ffa9582 ......... Outpoint TXID | 00000000 ................................. Outpoint index number: 0

fb4f0a00 ................................... Block pay height: 675835

Payee Address | 19 ....................................... Address Length: 25 | | 76 ..................................... OP_DUP | | a9 ..................................... OP_HASH160 | | 14 ..................................... Push 20 bytes as data | | | 1767c363646be7d8e4475c0aa85ea454 | | | 9fd102c4 ............................. Pubkey hash | | 88 ..................................... OP_EQUALVERIFY | | ac ..................................... OP_CHECKSIG

Masternode Signature | 41 ....................................... Bytes in signature: 65 | 1c25da47190a83937fb5ef607235703a | 7cdda155bf5a1ae6139929024750f899 | a90a4f57cdf9d54c9d9603c1f31009f8 | e257355b49c0484fb4c31bc412c73dd9 | 20 ....................................... Signature {% endhighlight %}

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mnwb

{% include helpers/subhead-links.md %}

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There is no message for mnwb (inv message only).

The following annotated hexdump shows an inv message with a mnwb inventory entry. (The message header has been omitted.)

{% highlight text %} 01 ................................. Count: 1

08000000 ........................... Type: MSG_MASTERNODE_PAYMENT_BLOCK (8) dd6cc6c11211793b239c2e311f1496e2 2281b200b35233eaae465d2aa3c9d537 ... Hash: mnwb {% endhighlight %}

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ssc

{% include helpers/subhead-links.md %}

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The ssc message is used to track the sync status of masternode objects. This message is sent in response to sync requests for the list of masternodes (dseg message), masternode payments (mnget message), governance objects (govsync message), and governance object votes (govsync message).

Bytes	Name	Data type	Required	Description
4	nItemID	int	Required	Masternode Sync Item ID
4	nCount	int	Required	Number of items to sync

Sync Item IDs

ID	Description	Response To
2	MASTERNODE_SYNC_LIST	dseg message
3	MASTERNODE_SYNC_MNW	mnget message
10	MASTERNODE_SYNC_GOVOBJ	govsync message
11	MASTERNODE_SYNC_GOVOBJ_VOTE	govsync message with non-zero hash

The following annotated hexdump shows a ssc message. (The message header has been omitted.)

{% highlight text %} 02000000 ................................... Item ID: MASTERNODE_SYNC_LIST (2) bf110000 ................................... Count: 4543 {% endhighlight %}

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Governance Messages

{% include helpers/subhead-links.md %}

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The following network messages enable the Governance features built in to Dash. For additional details on the governance system, see this Budget System page.

For additional details, refer to the Developer Guide Governance section.

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govobj

{% include helpers/subhead-links.md %}

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The govobj message contains a governance object that is generally a proposal, contract, or setting. Masternodes ignore this request if they are not fully synced.

Bytes	Name	Data type	Required	Description
32	nHashParent	uint256	Required	Parent object (a hash of all zeros here indicates this is the root object, not a child object).
4	nRevision	int	Required	Object revision in the system
8	nTime	int64_t	Required	Time which this object was created
32	nCollateralHash	uint256	Required*	Hash of the collateral fee transaction for proposals. Set to all zeros for Triggers/Watchdogs.
0-16384	strData	string	Required	Data field - can be used for anything (leading varint indicates size of data)
4	nObjectType	int	Required	Type of governance object: • 0 - Unknown • 1 - Proposal • 2 - Trigger • 3 - Watchdog
36	masternodeOutPoint	outPoint	Required*	The unspent outpoint of the masternode (holding 1000 DASH) which is signing this object. Set to all zeros for proposals since they can be created by non-masternodes.
66*	vchSig	char[]	Required*	Signature of the masternode (Length (1 byte) + Signature (65 bytes)) Not required for proposals - they will have a length of 0x00 and no Signature.

Governance Object Types (defined by src/governance-object.h)

Type	Name	Description
0	GOVERNANCE_OBJECT_UNKNOWN
1	GOVERNANCE_OBJECT_PROPOSAL	Submitted proposal (requires collateral transaction - currently 5 Dash)
2	GOVERNANCE_OBJECT_TRIGGER	Masternode generated. Removed after activation/execution. Used for superblocks.
3	GOVERNANCE_OBJECT_WATCHDOG	Masternode generated. Two hour expiration time. DEPRECATED since 12.2.

The following annotated hexdump shows a govobj message for a Proposal object. Notice the presence of a non-zero collateral hash, a masternodeOutPoint that is an empty Outpoint (hash of all zeros), and no vchSig. (The message header has been omitted.)

{% highlight text %} 00000000000000000000000000000000 00000000000000000000000000000000 ..... Parent Hash (0 = root) 01000000 ............................. Revision: 1 c8dfd65900000000 ..................... Create timestamp: 2017-10-06 01:43:31 UTC 633611d2f3e7481325242f200c7f3485 e3a9b4b6301e7f7d18d87d8231f3880b ..... Collateral Hash

Data | 3e02 ............................... Data length: 574 | 356235623232373 ... 376435643564 ... Data (truncated)

01000000 ............................. Object Type: GOVERNANCE_OBJECT_PROPOSAL (1)

Masternode Unspent Outpoint | 00000000000000000000000000000000 | 00000000000000000000000000000000 ... Outpoint TXID | ffffffff ........................... Outpoint index number: 0

00 ................................... Signature length: 0

| .................................... Masternode Signature (None required) {% endhighlight %}

The following annotated hexdump shows a govobj message for a Trigger object. Notice the collateral hash of all zeros. (The message header has been omitted.)

{% highlight text %} 00000000000000000000000000000000 00000000000000000000000000000000 ..... Parent Hash (0 = root) 01000000 ............................. Revision: 1 911ea85900000000 ..................... Create timestamp: 2017-08-31 14:34:57 UTC 00000000000000000000000000000000 00000000000000000000000000000000 ..... Collateral Hash (None required)

Data | ae11 ............................... Data length: 4526 | fdae11356235623 ... 376435643564 ... Data (truncated)

02000000 ............................. Object Type: GOVERNANCE_OBJECT_TRIGGER (2)

Masternode Unspent Outpoint | ffefbe4959085907bcd2ba29e357a441 | fa7b6e26e25896d8127332bba2419e97 ... Outpoint TXID | 00000000 ........................... Outpoint index number: 0

41 ................................... Signature length: 65

1ce3b782f66be8ae9fc4158680128864 341202b6006384083ab2d9cfa73795e2 6000668e84af4ef6a284a52b53843524 72037d51bd9079ffd5c087d9632865ee 75 ................................... Masternode Signature {% endhighlight %}

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govobjvote

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The govobjvote message is used to indicate the voting status of a governance object. Voting status is comprised of the vote outcome (how the masternode voted) and the vote signal (the network support status). A sufficient number of yes votes results in the proposed funding being payed out in the next superblock (assuming their are sufficient funds available in the budget).

The initial govobjvote message is created by a masternode to vote on a governance object (proposal, etc.). When the masternode votes, it broadcasts the govobjvote message to all its peers.

When a node receives a valid, new govobjvote message, it relays the message to all its connected peers to propagate the vote.

Additionally, nodes can request govobjvote messages for specific governance objects via a govsync message. Masternodes ignore requests for votes if they are not fully synced.

{% highlight text %} Dash Core limits how frequently a masternode can vote on a governance object. A masternode's vote will not be processed if it has been less than 60 minutes since its last vote on that object. Additionally, invalid votes can result in the node being banned. {% endhighlight %}

Bytes	Name	Data type	Required	Description
36	masternodeOutPoint	outPoint	Required	The unspent outpoint of the masternode (holding 1000 DASH) which is voting
32	nParentHash	uint256	Required	Object (govobj) being voted on (proposal, contract, setting or final budget)
4	nVoteOutcome	int	Required	None (0), Yes (1), No (2), Abstain (3)
4	nVoteSignal	int	Required	None (0), Funding (1), Valid (2), Delete (3), Endorsed (4)
8	nTime	int64_t	Required	Time the vote was created
66*	vchSig	char[]	Required	Signature of the masternode (66 bytes in most cases. Length (1 byte) + Signature (65 bytes))

Governance Object Vote Signals (defined by src/governance-object.h)

Value	Name	Description
1	Funding	Minimum network support has been reached for this object to be funded (doesn't mean it will for sure though)
2	Valid	Minimum network support has been reached flagging this object as a valid and understood governance object (e.g, the serialized data is correct format, etc.)
3	Delete	Minimum network support has been reached saying this object should be deleted from the system entirely
4	Endorsed	Minimum network support has been reached flagging this object as endorsed by an elected representative body

The following annotated hexdump shows a govobjvote message. (The message header has been omitted.)

{% highlight text %} Masternode Unspent Outpoint | 57566a0ef85e6cac3415ced67b0b07e1 | 781bafb853650d7c9d56d8bc132cc3b4 ... Outpoint TXID | 00000000 ........................... Outpoint index number: 0

ad9579d5c181eee904156df1c88b050f b8b4d39e5fda71f015996dbf14a51bff...... Parent Hash (0 = root) 01000000 ............................. Vote Outcome: VOTE_OUTCOME_NONE (1) 02000000 ............................. Vote Signal: VOTE_SIGNAL_VALID (2) b517a85900000000 ..................... Vote Create Timestamp: 2017-08-31 14:05:41 UTC 00000000000000000000000000000000 ..... Collateral Hash

1b049113a81fe913f061ad295561d267 00b8135a021ab0356a1e89b18d663d0b dc45e9c09ee0427223e332b52e8d709e 6d64e86b6435d7bdf207d8f23b6ae0db 6f ................................... Masternode Signature {% endhighlight %}

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govsync

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The govsync message is used to request syncing of governance objects (govobj message and govobjvote message) with peers. Masternodes ignore this request if they are not fully synced.

This message responds in one of two ways depending on the request:

1. Object Sync - When a masternode receives a govsync message with a hash of all zeros, it responds with one ssc message for govobj objects and one for govobjvote objects. The masternode also sends an inv message (MSG_GOVERNANCE_OBJECT - 0x17) for all valid govobj governance objects. Governance object votes are excluded in this type of response.

2. Vote Sync - When a masternode receives a govsync message with a specific hash, it responds with one ssc message for govobj objects and one for govobjvote objects. The masternode also sends both a govobj inventory message (MSG_GOVERNANCE_OBJECT - 0x17) and govobjvote inventory messages (MSG_GOVERNANCE_OBJECT_VOTE - 0x18) for the single governance object requested.

Bytes	Name	Data type	Required	Description
32	nHash	uint256	Required	Hash of governance object to request Set to all zeros to request all objects (excludes votes)
#	filter	CBloomFilter	Required	Can be set to all zeros. Only supported since [protocol version 70206][section protocol versions]

{% highlight text %} Dash Core limits how frequently the first type of sync (object sync) can be requested. Frequent requests will result in the node being banned. {% endhighlight %}

The following annotated hexdump shows a govsync message. (The message header has been omitted.)

{% highlight text %} 2e46ea5418e097a3dbcccbee3cf2a911 6fb94ba635153f276dcb2123efcb73ff ..... Hash 00000000000000000000 ................. Bloom Filter {% endhighlight %}

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Deprecated Messages

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The following network messages have been deprecated and should no longer be used.

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mnvs

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Masternode Budget Sync - Deprecated since 12.1

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mvote

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Masternode Budget Vote - Deprecated since 12.1

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mprop

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Masternode Budget Proposal - Deprecated since 12.1

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fbs

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Masternode Budget Final - Deprecated since 12.1

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fbvote

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Masternode Budget Final Vote - Deprecated since 12.1

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mn quorum

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Not Implemented

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