Tendermint Socket Protocol (TMSP)

Blockchains are a system for creating shared multi-master application state. TMSP is a socket protocol enabling a blockchain consensus engine, running in one process, to manage a blockchain application state, running in another.

For more information on TMSP, motivations, and tutorials, please visit our blog post.

Other implementations:

• cpp-tmsp by Martin Dyring-Andersen
• js-tmsp

Message format

Since this is a streaming protocol, all messages are encoded with a length-prefix followed by the message encoded in Protobuf3. Protobuf3 doesn't have an official length-prefix standard, so we use our own. The first byte represents the length of the big-endian encoded length.

For example, if the Protobuf3 encoded TMSP message is 0xDEADBEEF (4 bytes), the length-prefixed message is 0x0104DEADBEEF. If the Protobuf3 encoded TMSP message is 65535 bytes long, the length-prefixed message would be like 0x02FFFF....

Message types

TMSP requests/responses are simple Protobuf messages. Check out the schema file.

AppendTx

• Arguments:
  • Data ([]byte): The request transaction bytes
• Returns:
  • Code (uint32): Response code
  • Data ([]byte): Result bytes, if any
  • Log (string): Debug or error message
• Usage:
  Append and run a transaction. If the transaction is valid, returns CodeType.OK

CheckTx

• Arguments:
  • Data ([]byte): The request transaction bytes
• Returns:
  • Code (uint32): Response code
  • Data ([]byte): Result bytes, if any
  • Log (string): Debug or error message
• Usage:
  Validate a transaction. This message should not mutate the state. Transactions are first run through CheckTx before broadcast to peers in the mempool layer. You can make CheckTx semi-stateful and clear the state upon Commit or BeginBlock, to allow for dependent sequences of transactions in the same block.

Commit

• Returns:
  • Data ([]byte): The Merkle root hash
  • Log (string): Debug or error message
• Usage:
  Return a Merkle root hash of the application state.

Query

• Arguments:
  • Data ([]byte): The query request bytes
• Returns:
  • Code (uint32): Response code
  • Data ([]byte): The query response bytes
  • Log (string): Debug or error message

Flush

• Usage:
  Flush the response queue. Applications that implement types.Application need not implement this message -- it's handled by the project.

Info

• Returns:
  • Data ([]byte): The info bytes
• Usage:
  Return information about the application state. Application specific.

SetOption

• Arguments:
  • Key (string): Key to set
  • Value (string): Value to set for key
• Returns:
  • Log (string): Debug or error message
• Usage:
  Set application options. E.g. Key="mode", Value="mempool" for a mempool connection, or Key="mode", Value="consensus" for a consensus connection. Other options are application specific.

InitChain

• Arguments:
  • Validators ([]Validator): Initial genesis validators
• Usage:
  Called once upon genesis

BeginBlock

• Arguments:
  • Height (uint64): The block height that is starting
• Usage:
  Signals the beginning of a new block. Called prior to any AppendTxs.

EndBlock

• Arguments:
  • Height (uint64): The block height that ended
• Returns:
  • Validators ([]Validator): Changed validators with new voting powers (0 to remove)
• Usage:
  Signals the end of a block. Called prior to each Commit after all transactions

Changelog

Mar 26h, 2016

• Introduce BeginBlock

Mar 6th, 2016

• Added InitChain, EndBlock

Feb 14th, 2016

• s/GetHash/Commit/g
• Document Protobuf request/response fields

Jan 23th, 2016

• Added CheckTx/Query TMSP message types
• Added Result/Log fields to AppendTx/CheckTx/SetOption
• Removed Listener messages
• Removed Code from ResponseSetOption and ResponseGetHash
• Made examples BigEndian

Jan 12th, 2016

• Added "RetCodeBadNonce = 0x06" return code

Jan 8th, 2016

• Tendermint/TMSP now comes to consensus on the order first before AppendTx.