upstream-jitsi-videobridge/doc/datachannel-communication.md

Messages by COLIBRI class:

EndpointMessage:

This type of messages could be used by the clients for sending JSON objects to the other clients in the conference. A client can send a message to specific endpoint or a broadcast message.

• The messages processed by Jitsi Videobridge has the following format:

{
    colibriClass: "EndpointMessage",  
    to: `<ENDPOINT-ID>`,   
    msgPayload: `<PAYLOAD>`  
}

<PAYLOAD> is valid JSON string.
<ENDPOINT-ID> is endpoint id of existing participant or "" for broadcast message.

• The messages sent by Jitsi Videobridge has the following format:

{
    colibriClass: "EndpointMessage",
    to: `<ENDPOINT-ID>`,
    from: `<ENDPOINT-ID>`,
    msgPayload: <PAYLOAD>
}

The only modification made by Jitsi Videobridge before the message is forwarded is adding from property to it. The value of this property is the endpoint id of the sender of the message.