文章目录

• example说明
• • 整体流程
• 源码
• • 拆解
  • • server
    • • 打开本地的udp listener
      • 通过setting engine设置listener
      • 托管本地index
      • 接受client sdp的http接口
      • • doSignaling
      • 启动http服务
    • client
    • • 创建datachannel
      • 打印远端candidate信息
      • 创建本地sdp，发送给服务器，并设置服务器sdp

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udpListener, err := net.ListenUDP("udp", &net.UDPAddr{  IP:   net.IP{0, 0, 0, 0},  Port: 8443,
})
if err != nil {  panic(err)
}

// Create a SettingEngine, this allows non-standard WebRTC behavior
// 创建SettingEngine，通过SettingEnginen，能够允许非标准的WebRTC流程，比如说固定ice的端口
settingEngine := webrtc.SettingEngine{}  // Configure our SettingEngine to use our UDPMux. By default a PeerConnection has
// no global state. The API+SettingEngine allows the user to share state between them.
// In this case we are sharing our listening port across many.
// 设置UDPMux，即UDP复用器，允许不同的peer connection共享相同的端口
settingEngine.SetICEUDPMux(webrtc.NewICEUDPMux(nil, udpListener))  // Create a new API using our SettingEngine
// 使用settingEngine创建webrtc api。后续可以通过这个api完成双向通信
// 这个api是个全局变量，可以在接收到远端的sdp offer之后调用处理
api = webrtc.NewAPI(webrtc.WithSettingEngine(settingEngine))

http.Handle("/", http.FileServer(http.Dir(".")))

http.HandleFunc("/doSignaling", doSignaling)

POST /doSignaling HTTP1.1{"type": "offer","sdp": "<sdp string>"
}

{"type": "answer","sdp": "<sdp string>"
}

func doSignaling(w http.ResponseWriter, r *http.Request) {  peerConnection, err := api.NewPeerConnection(webrtc.Configuration{})  if err != nil {  panic(err)  }  // Set the handler for ICE connection state  // This will notify you when the peer has connected/disconnected peerConnection.OnICEConnectionStateChange(func(connectionState webrtc.ICEConnectionState) {  fmt.Printf("ICE Connection State has changed: %s\n", connectionState.String())  })  // Send the current time via a DataChannel to the remote peer every 3 seconds  peerConnection.OnDataChannel(func(d *webrtc.DataChannel) {  d.OnOpen(func() {  for range time.Tick(time.Second * 3) {  if err = d.SendText(time.Now().String()); err != nil {  panic(err)  }  }  })  })  var offer webrtc.SessionDescription  if err = json.NewDecoder(r.Body).Decode(&offer); err != nil {  panic(err)  }  if err = peerConnection.SetRemoteDescription(offer); err != nil {  panic(err)  }  // Create channel that is blocked until ICE Gathering is complete  gatherComplete := webrtc.GatheringCompletePromise(peerConnection)  answer, err := peerConnection.CreateAnswer(nil)  if err != nil {  panic(err)  } else if err = peerConnection.SetLocalDescription(answer); err != nil {  panic(err)  }  // Block until ICE Gathering is complete, disabling trickle ICE// we do this because we only can exchange one signaling message// in a production application you should exchange ICE Candidates via OnICECandidate<-gatherComplete  response, err := json.Marshal(*peerConnection.LocalDescription())  if err != nil {  panic(err)  }  w.Header().Set("Content-Type", "application/json")  if _, err := w.Write(response); err != nil {  panic(err)  }
}

panic(http.ListenAndServe(":8080", nil))

let pc = new RTCPeerConnection()
let dc = pc.createDataChannel('data')

dc.onopen = () => {  let el = document.createElement('template')  let selectedPair = pc.sctp.transport.iceTransport.getSelectedCandidatePair()  el.innerHTML = `<div>  <ul> <li> <i> Local</i> - ${selectedPair.local.candidate}</li>  <li> <i> Remote</i> - ${selectedPair.remote.candidate} </li> </ul> </div>`document.getElementById('iceSelectedPairs').appendChild(el.content.firstChild);
}

pc.createOffer()  .then(offer => {  pc.setLocalDescription(offer)  return fetch(`/doSignaling`, {  method: 'post',  headers: {  'Accept': 'application/json, text/plain, */*',  'Content-Type': 'application/json'  },  body: JSON.stringify(offer)  })  })  .then(res => res.json())  .then(res => pc.setRemoteDescription(res))  .catch(alert)