Intercessor

Peer Messaging Service

Intercessor is a relay server to exchange messages between two peers. Intercessor is initially designed as a signaling server for WebRTC. It is similar to SignalMaster.

A server first connects to the Intercessor (the relay), and receives back a unique token that can be used by the client(s) to connect to the Intercessor.

• Server connection: wss://somehost/server
• Client connection: wss://somehost/client/SERVER_ID

Developing

To submit changes for review, push them to a branch in a fork and submit a pull request to merge that branch into main.

Logging

Log level can be specified as an environmnt variable such as:

RUST_LOG=trace cargo run

Protocol

Messsage Format

Peers must send messages in the following format:

{
    "to": PEER_ID,
    "type": MESSAGE_TYPE,
    "message": MESSAGE
}

Messages sent from the relay have the following format:

{
    "from": PEER_ID,
    "type": MESSAGE_TYPE,
    "message": MESSAGE
}

Where:

• PEER_ID (string): The unique identifier of the peer.
• MESSAGE_TYPE (string): The type of content of the message. Either 'HELLO', 'PEER_JOINED', "PEER_GONE", or application specific.
• MESSAGE (Object): The actual message content (HELLO, PEER_JOINED, PEER_GONE, or other message).

HELLO message

When a peer connects to the Intercessor, it will receive a HELLO message with the following content:

{
    "id": USER_ID,
    "serverInfo": SERVER_INFO
}

Where:

• USER_ID (string): The unique ID attributed to the peer.
• SERVER_INFO (string): Optional application specific information configured on the server.

PEER_JOINED message

This message is sent to a server when a new client connects using its server ID.

{
    "id": USER_ID
}

Where:

• USER_ID (string): The unique ID of the new client.

PEER_GONE message

This message is sent to a peer when their peer leaves.

{
    "id": USER_ID
}

Where:

• USER_ID (string): The unique ID of the peer that has left.

Future

This project is a work in progress. Future work includes the following:

• SSL Support
• Command-line & file configuration
• Server extra info in HELLO message
• Passphrase for server logins
• Replace UUID with something stronger and/or easier to remember
• Client timeouts
• Apply optional (configurable) schema validation on messages sent by the peers
• Valgrind
• Docker image