如何在 Chrome 中为 WebRTC 呼叫者设置远程描述而不会出错？

Question

希望逻辑没有漏洞

第 1 步： 来电者创建报价

步骤 2： 调用者设置 localDescription

第 3 步： 调用者将描述发送给被调用者

//---------------------------------------- ----------//

第 4 步： 被叫方接收报价设置远程描述

第 5 步： 被叫方创建应答

第 6 步： 被叫方设置本地描述

第 7 步： 被叫方将描述发送给来电方

//---------------------------------------- ----------//

第 8 步： 调用方收到应答并设置远程描述

这是上面的代码

const socket = io();
const constraints = {
  audio: true,
  video: true
};
const configuration = {
  iceServers: [{
    "url": "stun:23.21.150.121"
  }, {
    "url": "stun:stun.l.google.com:19302"
  }]
};

const selfView = $('#selfView')[0];
const remoteView = $('#remoteView')[0];

var pc = new RTCPeerConnection(configuration);

pc.onicecandidate = ({
  candidate
}) => {
  socket.emit('message', {
    to: $('#remote').val(),
    candidate: candidate
  });
};

pc.onnegotiationneeded = async () => {
  try {
    await pc.setLocalDescription(await pc.createOffer());
    socket.emit('message', {
      to: $('#remote').val(),
      desc: pc.localDescription
    });
  } catch (err) {
    console.error(err);
  }
};

pc.ontrack = (event) => {
  // don't set srcObject again if it is already set.
  if (remoteView.srcObject) return;
  remoteView.srcObject = event.streams[0];
};

socket.on('message', async ({
  from,
  desc,
  candidate
}) => {
  $('#remote').val(from);
  try {
    if (desc) {
      // if we get an offer, we need to reply with an answer
      if (desc.type === 'offer') {
        await pc.setRemoteDescription(desc);
        const stream = await navigator.mediaDevices.getUserMedia(constraints);
        stream.getTracks().forEach((track) => pc.addTrack(track, stream));
        selfView.srcObject = stream;
        await pc.setLocalDescription(await pc.createAnswer());
        console.log(pc.localDescription);
        socket.emit({
          to: from,
          desc: pc.localDescription
        });
      } else if (desc.type === 'answer') {
        await pc.setRemoteDescription(desc).catch(err => console.log(err));
      } else {
        console.log('Unsupported SDP type.');
      }
    } else if (candidate) {
      await pc.addIceCandidate(new RTCIceCandidate(candidate)).catch(err => console.log(err));
    }
  } catch (err) {
    console.error(err);
  }
});


async function start() {
  try {
    // get local stream, show it in self-view and add it to be sent
    const stream = await requestUserMedia(constraints);
    stream.getTracks().forEach((track) => pc.addTrack(track, stream));
    attachMediaStream(selfView, stream);
  } catch (err) {
    console.error(err);
  }
}

socket.on('id', (data) => {
  $('#myid').text(data.id);
});


// this function is called once the caller hits connect after inserting the unique id of the callee
async function connect() {
  try {
    await pc.setLocalDescription(await pc.createOffer());
    socket.emit('message', {
      to: $('#remote').val(),
      desc: pc.localDescription
    });
  } catch (err) {
    console.error(err);
  }
}

socket.on('error', data => {
  console.log(data);
});

现在这段代码在执行步骤 8

时抛出错误

DOMException: Failed to execute 'setRemoteDescription' on 'RTCPeerConnection': Failed to set remote offer sdp: Called in wrong state: kHaveLocalOffer

DOMException: Failed to execute 'addIceCandidate' on 'RTCPeerConnection': Error processing ICE candidate

尝试调试但未发现逻辑或代码中的任何缺陷。注意到 pc 对象具有 localDescription 和 currentLocalDescription 的一件奇怪的事情，我认为创建答案的被调用者必须同时具有描述类型 answer 而是显示localDescription 为 offer 并且 currentLocalDescription 类型为 answer.

我不知道它是否应该像我初学者那样表现。

提前致谢。

Answer 1

您的代码是正确的。这是一个长期 bug in Chrome 和 negotiationneeded.

我在 a fiddle 中对其进行了检测（右键单击并打开相邻的两个 windows，然后单击调用其中一个）。

在 Firefox 中，它可以工作。报价方协商一次，因为您一次添加了两条轨道（video/audio）：

negotiating in stable
onmessage answer

并且，在回答者方面，您在 'stable' 状态之外添加的曲目将添加到答案中：

onmessage offer
adding audio track
adding video track

但在 Chrome 中，它坏了，在提供者上发射 negotiationneeded 两次，每添加一个曲目一次：

negotiating in stable
negotiating in stable
onmessage offer
DOMException: Failed to execute 'setRemoteDescription' on 'RTCPeerConnection':
  Failed to set remote offer sdp: Called in wrong state: kHaveLocalOffer
onmessage offer
DOMException: Failed to execute 'setRemoteDescription' on 'RTCPeerConnection':
  Failed to set remote offer sdp: Called in wrong state: kHaveLocalOffer
onmessage offer
DOMException: Failed to execute 'setRemoteDescription' on 'RTCPeerConnection':
  Failed to set remote offer sdp: Called in wrong state: kHaveLocalOffer

并在应答端触发 negotiationneeded 两次，甚至不在 'stable' 状态：

onmessage offer
adding audio track
adding video track
negotiating in have-remote-offer
negotiating in have-remote-offer
onmessage offer
DOMException: Failed to execute 'setRemoteDescription' on 'RTCPeerConnection':
  Failed to set remote offer sdp: Called in wrong state: kHaveLocalOffer

这些额外的事件导致两端出现相互状态错误的严重破坏。

具体来说，Chrome 在这里违反了 spec 的两个部分：

"Queue a task" 来触发这个事件。 "queueing prevents negotiationneeded from firing prematurely, in the common situation where multiple modifications to connection are being made at once."
如果连接的信号状态不是 "stable"，则中止这些步骤[以触发事件]。

解决方法

解决两个 Chrome 错误需要（为简洁起见使用async/await）：

let negotiating = false;
pc.onnegotiationneeded = async e => {
  try {
    if (negotiating || pc.signalingState != "stable") return;
    negotiating = true;
    /* Your async/await-using code goes here */
  } finally {
    negotiating = false;
  }
}

如何在 Chrome 中为 WebRTC 呼叫者设置远程描述而不会出错？

How to set remote description for a WebRTC caller in Chrome without errors?

javascript

webrtc

sdp

peer-connection

rtcpeerconnection

解决方法