> ## Documentation Index
> Fetch the complete documentation index at: https://docs.navtalk.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# webrtc.signaling.answer

> WebRTC answer signaling event

Triggered when a WebRTC answer is received through the unified WebSocket connection. This is the response to a WebRTC offer.

## Event Properties

<ResponseField name="type" type="string">
  Event type. Always `"webrtc.signaling.answer"` for this event.
</ResponseField>

<ResponseField name="data" type="object">
  Event data object containing WebRTC answer information.
</ResponseField>

<ResponseField name="data.sdp" type="object">
  The SDP (Session Description Protocol) answer object. This is an RTCSessionDescription object that needs to be set as the remote description.

  **Example**:

  ```json theme={null}
  {
    "type": "answer",
    "sdp": "v=0\r\no=- 123456789 123456789 IN IP4 0.0.0.0\r\n..."
  }
  ```
</ResponseField>

<ResponseExample>
  ```json Example theme={null}
  {
    "type": "webrtc.signaling.answer",
    "data": {
      "sdp": {
        "type": "answer",
        "sdp": "v=0\r\no=- 123456789 123456789 IN IP4 0.0.0.0\r\n..."
      }
    }
  }
  ```
</ResponseExample>

## Sending Answer

After receiving a WebRTC offer, you need to create an answer and send it back. Here's how to send the answer:

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

// Function to send answer
function sendAnswerMessage(sdp) {
    const message = {
        type: NavTalkMessageType.WEB_RTC_ANSWER,
        data: { sdp: sdp }
    };
    socket.send(JSON.stringify(message));
    console.log('Sent answer:', message);
}

// Handle received offer and send answer
async function handleOffer(offerData) {
    const offer = new RTCSessionDescription(offerData.sdp);
    peerConnection = new RTCPeerConnection(configuration);
    
    await peerConnection.setRemoteDescription(offer);
    const answer = await peerConnection.createAnswer();
    await peerConnection.setLocalDescription(answer);
    
    // Send the answer (peerConnection.localDescription is an RTCSessionDescription object)
    sendAnswerMessage(peerConnection.localDescription);
}
```

**Message Structure:**

When sending an answer, the message structure should be:

```json theme={null}
{
  "type": "webrtc.signaling.answer",
  "data": {
    "sdp": {
      "type": "answer",
      "sdp": "v=0\r\no=- 8643312983218886913 2 IN IP4 127.0.0.1\r\ns=-\r\nt=0 0\r\na=group:BUNDLE 0 1\r\na=msid-semantic: WMS\r\nm=video 9 UDP/TLS/RTP/SAVPF 97 98 99 100 101 102\r\nc=IN IP4 0.0.0.0\r\na=rtcp:9 IN IP4 0.0.0.0\r\na=ice-ufrag:lwyK\r\na=ice-pwd:DL6EkCNVmdcrlsmJsjry5CiG\r\na=ice-options:trickle\r\na=fingerprint:sha-256 FE:A4:ED:91:41:78:BB:35:7D:CC:77:36:84:05:60:5D:6F:12:0A:B0:0E:A1:94:DA:90:3B:EF:6F:39:56:7F:E0\r\na=setup:active\r\na=mid:0\r\na=extmap:3 http://www.webrtc.org/experiments/rtp-hdrext/abs-send-time\r\na=extmap:1 urn:ietf:params:rtp-hdrext:sdes:mid\r\na=recvonly\r\na=rtcp-mux\r\na=rtpmap:97 VP8/90000\r\na=rtcp-fb:97 goog-remb\r\na=rtcp-fb:97 nack\r\na=rtcp-fb:97 nack pli\r\na=rtpmap:98 rtx/90000\r\na=fmtp:98 apt=97\r\na=rtpmap:99 H264/90000\r\na=rtcp-fb:99 goog-remb\r\na=rtcp-fb:99 nack\r\na=rtcp-fb:99 nack pli\r\na=fmtp:99 level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=42001f\r\na=rtpmap:100 rtx/90000\r\na=fmtp:100 apt=99\r\na=rtpmap:101 H264/90000\r\na=rtcp-fb:101 goog-remb\r\na=rtcp-fb:101 nack\r\na=rtcp-fb:101 nack pli\r\na=fmtp:101 level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=42e01f\r\na=rtpmap:102 rtx/90000\r\na=fmtp:102 apt=101\r\nm=audio 9 UDP/TLS/RTP/SAVPF 96 9 0 8\r\nc=IN IP4 0.0.0.0\r\na=rtcp:9 IN IP4 0.0.0.0\r\na=ice-ufrag:lwyK\r\na=ice-pwd:DL6EkCNVmdcrlsmJsjry5CiG\r\na=ice-options:trickle\r\na=fingerprint:sha-256 FE:A4:ED:91:41:78:BB:35:7D:CC:77:36:84:05:60:5D:6F:12:0A:B0:0E:A1:94:DA:90:3B:EF:6F:39:56:7F:E0\r\na=setup:active\r\na=mid:1\r\na=extmap:2 urn:ietf:params:rtp-hdrext:ssrc-audio-level\r\na=extmap:1 urn:ietf:params:rtp-hdrext:sdes:mid\r\na=recvonly\r\na=rtcp-mux\r\na=rtpmap:96 opus/48000/2\r\na=fmtp:96 minptime=10;useinbandfec=1\r\na=rtpmap:9 G722/8000\r\na=rtpmap:0 PCMU/8000\r\na=rtpmap:8 PCMA/8000\r\n"
    }
  }
}
```

**Key Points:**

* The `sdp` parameter in `data.sdp` should be an `RTCSessionDescription` object (or equivalent plain object) with:
  * `type`: `"answer"`
  * `sdp`: The SDP string containing the answer description
* Send the answer **immediately after** you receive an offer and create an answer using `peerConnection.createAnswer()`
* Use `peerConnection.localDescription` as the `sdp` value when sending

## Receiving Answer

When you receive an answer (if you sent an offer), handle it like this:

```javascript theme={null}
async function handleReceivedMessage(data) {
    const nav_data = data.data;
    
    switch (data.type) {
        case NavTalkMessageType.WEB_RTC_ANSWER:
            const answer = new RTCSessionDescription(nav_data.sdp);
            await peerConnection.setRemoteDescription(answer);
            break;
    }
}
```

<Note>
  * **When to send**: Send an answer immediately after receiving an offer and creating an answer with `peerConnection.createAnswer()`
  * **What to send**: Send `peerConnection.localDescription` (which is an RTCSessionDescription object) as the `sdp` value
  * WebRTC signaling is sent through the unified WebSocket connection
</Note>