Messages

Currently, version one of the Streamer Protocol supports only six message types:

Command	Purpose
0x00 HELLO	The HELLO message is the first message sent between the client and Mevlink node. It consists of the protocol version and user id.
0x01 CHALLENGE	The CHALLENGE message is consists of the 16-byte HMAC challenge string
0x02 CHALLENGE_RESPONSE	The CHALLENGE_RESPONSE consists of the HMAC-SHA256 digest using your API Key Secret
0x03 TRANSACTION	The TRANSACTION message includes the rlp encoded tx bytes, the unix timestamp of when tx was sent, and the unix timestamp of when mevlink first learned about the transaction.
0x04 DISCONNECT	The DISCONNECT message occurs before the connection is terminated and contains an error code
0x05 EMIT_TRANSACTION	Message to propagate a transaction.
Coming soon EMIT_WHITELIST	The EMIT_WHITELIST message explicitly tells the node which peers you'd like us to send the propagation request transactions to.
Coming soon EMIT_BLACKLIST	The EMIT_BLACKLIST message tells the node which peers not to send your propogation requests to, if any.

Hello

The HELLO message is the first message sent between the client and Mevlink node. It consists of the client's protocol version & their API Key ID, found in the Mevlink Dashboard.

	Length	Description
Command	1 byte	Message Type (0x00)
Protocol Version	1 byte	Currently only 0x00 is supported
API Key ID	16 bytes	The API Key ID for your Mevlink acocunt

Challenge

The CHALLENGE message is sent by the Mevlink node in response to the client's HELLO message. It contains the 16-byte HMAC challenge string.

	Length	Description
Command	1 byte	Message Type (0x01)
Challenge	16 bytes	The HMAC challenge

Challenge Response

The The CHALLENGE_RESPONSE consists of the HMAC-SHA256 digest

	Length	Description
Command	1 byte	Message Type (0x02)
MAC	32 bytes	The HMAC-SHA256 digest response

Transaction

Once the messages above have been exchanged, the Mevlink node will begin sending TRANSACTION messages to the client. The TRANSACTION message includes the rlp encoded tx bytes, the unix timestamp of when tx was sent, and the unix timestamp of when Mevlink first learned about the transaction.

All rlp encoded transactions in the ethereumplex include a length specifier near the beginning. BSC uses legacy transactions and thus are also rlp encoded. Check out the ethereum rlp docs for more details or checkout how we parse this message in our streamer-go library.

The ordering of the emitted fields, timing information, and MAC is such that you can choose to react to transactions before you have timing information or have verified the authentication signature.

	Length	Description
Command	1 byte	Message Type (0x03)
RLP encoded Transaction	variable size	The RLP encoded transaction bytes
Propegation Timestamp	8 bytes	Unix microsecond timestamp indicating when the Mevlink relay received and sent the transaction.
Noticed Timestamp	8 bytes	Unix microsecond timestamp indicating when Mevlink first learned about the transaction from other peers. Note that this may not be the earliest time any mevlink relay has heard about the transaction at time of sending.
MAC	32 bytes	The MAC authentication signature

Disconnect

If the Mevlink node disconnects gracefully, it will do so with a DISCONNECT message containing an error code describing why it closed the connection.

	Length	Description
Command	1 byte	Message Type (0x04)
Error Code	1 byte	error code

Emit Transaction

This feature is currently in beta and experiencing many updates and maintenance. We do not consider it's performance to be as strong as our transaction streaming service at the moment, but encourage you to try it as a value add.

If you'd like to propagate a transaction, you can send a EMIT_TRANSACTION message with the RLP encoded transaction bytes.

	Length	Description
Command	1 byte	Message Type (0x05)
RLP encoded transaction bytes	variable size	The HMAC-SHA256 digest response

Emit Whitelist

Not live! Coming soon.

The EMIT_WHITELIST message explicitly tells the node which peers you'd like us to send the propagation request transactions to.

	Length	Description
Command	1 byte	Message Type (0x06)
RLP encoded enodes	variable size	RLP encoded list of enodes

Emit Blacklist

Not live! Coming soon.

The EMIT_WHITELIST message explicitly tells the node which peers you'd like us to NOT send the propagation request transactions to.

	Length	Description
Command	1 byte	Message Type (0x07)
RLP encoded enodes	variable size	RLP encoded list of enodes