factorio-clusterio/docs/socket.md

Socket.io protocol

_{This document describes the protocol used between the master and slaves, and unless you're developing Clusterio it's probably not going to be very useful for you.}

The protocol is built on the socket.io library which lets mulitple streams be multiplexed in many different ways over the same connection and abstracts away reconnection logic. Unfortunately I've been unable to figure what the message delivery guarantees of the library is, so whether or not messages can be lost is still an unknown, I assume that messages are delivered as long as a connection is maintained or manages to reconnect.

While there are many mechanisms to multiplex streams, the core communication between the master server and slaves is done entirely by sending single POJO payloads over the message event. There's a shortcut for sending these via the .send method of the socket.io sockets.

These messages contain the following three properties:

• seq - integer - The sequence number of the message
• type - string - The type of message
• data - object - Message data

Handshake

Upon connecting to the socket.io endpoint the server will respond with a hello message containing the master server version as the data. The client is then expected to send a register_slave or register_control message back depending on what kind of client it is. If the register operation is successful the master will reply with a ready message with an empty data payload.

Master hello data

• version - string - The version of the master, e.g. "2.0.0".

Slave register_slave response data

• agent - string - Human readable identifying the software connecting.
• version - string - The protocol version of the slave, e.g. "2.0.0".
• name - string - Name of the slave.
• id - integer - ID of the slave.

Control `register_control repsonse data

• agent - string - Human readable identifying the software connecting.
• version - string - The protocol version of the control, e.g. "2.0.0".

Example handshake

// Server hello
({
    type: 'hello',
    data: {
        version: "2.0.0",
    }
})

// Client response
({
    type: 'register_slave',
    data: {
        agent: 'Clusterio Slave',
        version: "2.0.0",
        name: "Foo",
        id: 123,
    }
})

// Server repsonse
({
    type: 'ready',
    data: {}
})

Requests

Requests are messages which expects a response in return. They function a lot like HTTP requests except that both parties of a connection can inniate a request that is expected to be responded to. By convention message types ending in *_request is a request, and is expected to be replied to with a corresponding *_response message. If an error occured while processing the request an error response containing an error property in the data payload is sent instead.

*_response data

• seq - integer - The seq number of the request message.
• additional properties may be present depending on the type of request.

*_resopnse error data

• seq - integer - The seq number of the request message.
• error - string - Human readable text message describing the error.

See lib/link/requests.js for the recognized requests and their implementation.

Closing the connection

The party that innitates the shut down of the connection should send a close message containing the reason for closing before disconnecting.

close data

• reason - string - Reason for closing the connection