livekit/docs/protocol.md

Signaling Protocol

LiveKit uses a websocket connection for signaling. Each client should start the RTC session by connecting to /rtc.

Joining a room

Handling negotiations

Negotiation is how WebRTC makes changes to the current communication, including adding/removing tracks. In WebRTC, either side could initiate the change and it makes synchronization a challenge.

In LiveKit, we've added a layer of synchronization so that negotiations are more deterministic. The server becomes the place to control who should be issuing offers in a negotiation cycle. When the client wants to issue an offer to the server after the initial connection is made, this is the flow

1. client's onnegotiationneeded callback is triggered
2. client sends server a NegotiationRequest
3. server determines when it's ready for a new offer, and notifies client with NegotiationResponse
4. when client receives NegotiationResponse, it generates a new offer and sends it as an offer in the form of SessionDescription.
5. server accepts the offer and sends an answer
6. client calls setRemoteDescription with that session description.

now the negotiation is complete and track changes have been applied.

Subscribing to tracks

Publishing tracks