webrtc.signaling.offer

WebRTC offer signaling event

Triggered when a WebRTC offer is received through the unified WebSocket connection. WebRTC signaling is sent through the same WebSocket connection as other events, eliminating the need for a separate WebRTC signaling connection.

Event Properties

type · string

Event type. Always "webrtc.signaling.offer" for this event.

data · object

Event data object containing WebRTC offer information.

data.sdp · object

The SDP (Session Description Protocol) offer object. This is an RTCSessionDescription object that needs to be set as the remote description.

Example:

{
  "type": "offer",
  "sdp": "v=0\r\no=- 123456789 123456789 IN IP4 0.0.0.0\r\n..."
}

Example

{
  "type": "webrtc.signaling.offer",
  "data": {
    "sdp": {
      "type": "offer",
      "sdp": "v=0\r\no=- 123456789 123456789 IN IP4 0.0.0.0\r\n..."
    }
  }
}

Receiving Offer

When you receive a WebRTC offer (typically sent by the server), handle it like this:

const NavTalkMessageType = Object.freeze({
    WEB_RTC_OFFER: "webrtc.signaling.offer",
    WEB_RTC_ANSWER: "webrtc.signaling.answer",
    WEB_RTC_ICE_CANDIDATE: "webrtc.signaling.iceCandidate",
    // ... other event types
});

// Function to send answer (after receiving offer)
function sendAnswerMessage(sdp) {
    const message = {
        type: NavTalkMessageType.WEB_RTC_ANSWER,
        data: { sdp: sdp }
    };
    socket.send(JSON.stringify(message));
}

// Function to send ICE candidate
function sendIceMessage(candidate) {
    const message = {
        type: NavTalkMessageType.WEB_RTC_ICE_CANDIDATE,
        data: { candidate: candidate }
    };
    socket.send(JSON.stringify(message));
}

async function handleReceivedMessage(data) {
    const nav_data = data.data;
    
    switch (data.type) {
        case NavTalkMessageType.WEB_RTC_OFFER:
            // Create peer connection
            const offer = new RTCSessionDescription(nav_data.sdp);
            peerConnection = new RTCPeerConnection(configuration);
            
            // Set remote description and create answer
            await peerConnection.setRemoteDescription(offer);
            const answer = await peerConnection.createAnswer();
            await peerConnection.setLocalDescription(answer);
            
            // Send answer through unified WebSocket
            sendAnswerMessage(peerConnection.localDescription);
            
            // Set up ICE candidate handler
            peerConnection.onicecandidate = (event) => {
                if (event.candidate) {
                    sendIceMessage(event.candidate);
                }
            };
            break;
    }
}

Key Points:

• The sdp parameter in data.sdp is an RTCSessionDescription object with:
  • type: "offer"
  • sdp: The SDP string containing the offer description
• After receiving an offer, you should:
  1. Create an RTCPeerConnection
  2. Set the offer as remote description
  3. Create and send an answer
  4. Set up ICE candidate handler to send candidates

• When received: The server typically sends the offer when establishing a WebRTC connection
• What to do: After receiving an offer, create an answer and send it back, then send ICE candidates as they’re generated
• All WebRTC signaling (offer, answer, ICE candidates) is sent through the unified WebSocket connection using the encapsulated event types. There is no need for a separate WebRTC signaling WebSocket connection.