Message Protocol

This section describes the message design between nodes, including message exchange formats and protocols.

Message Exchange Format

protobuf is the message exchange format between nodes. protobuf is a flexible and efficient data serialization method for structured data. It has the advantage of high-speed efficiency and space efficiency, e.g., small encode volume, fast encoding and decoding speed.

Message Protocol

A general message is the information that must be carried in all node communication. The message includes the following details of a peer node: version number, timestamp, message ID, whether to gossip this message to neighboring nodes, node ID, node public key, and node data signature. The primary function of a general message is to verify the node's identity and data signature. The general message protocol design is as follows:

message MessageData {
  string clientVersion = 1; // client version
  int64 timestamp = 2;      // unix timestamp
  string id = 3;            // allows requesters to use request data when processing a response
  bool gossip = 4;          // true to have receiver peer gossip the message to neighbors
  string nodeId = 5;        // id of node that created the message (not the peer that may have sent it). =base58(multihash(nodePubKey))
  bytes nodePubKey = 6;     // Authoring node Secp256k1 public key (32bytes) - protobufs serielized
  bytes sign = 7;           // signature of message data + method specific data by message authoring node.
}

Write Data Message Protocol

The write data message protocol describes how a node writes its data to another node, including request and response message formats. The write data message protocol is defined as follows:

message WritefileRequest {
  MessageData messageData = 1;
  string Roothash =2;  // Roothash uniquely identifies a user data
  string Datahash = 3; // Datahash is the currently written data hash value
  uint32 Length = 4;   // Length is the length of the data written this time
  uint32 Offset = 5;   // Offset is the offset of this write
  bytes Data = 6;      // Data is the data written this time
}

message WritefileResponse {
  MessageData messageData = 1;
  uint32 Code = 2;  // Code indicates the result of this transfer
  uint32 Offset =3; // Offset is the write offset the receiver wants
}

WritefileRequest defines the data offset of writing, which enables breakpoint and continuation setup in the writing process. As long as the peer informs the writer about the offset in WritefileResponse message, the writer can start writing from the position specified by the offset without having to start writing from the starting position every time.

Read Data Message Protocol

The read data message protocol describes how a node reads the desired data from another node, including request and response message formats. The read data message protocol is defined as follows:

message ReadfileRequest {
  MessageData messageData = 1;
  string Roothash =2;   // Roothash uniquely identifies a user data
  string Datahash = 3;  // Datahash is the currently written data hash value
  uint32 Offset = 4;    // Offset is the offset that the reader wants to read
}

message ReadfileResponse {
  MessageData messageData = 1;
  uint32 Code = 2;   // Code indicates the result of this transfer
  uint32 Offset =3;  // Offset is the data offset returned by the peer
  uint32 Length = 4; // Length is the returned data length
  bytes Data = 5;    // Data is the returned data
}

ReadfileRequest defines the data offset of reading, which enables breakpoint and continuation setup in the reading process. As long as the reader informs the peer about the offset in ReadfileResponse message, the peer can start reading from the position specified by the offset.