Google WebRtc Android 使用详解(包括客户端和服务端代码)

转自：https://zhuanlan.zhihu.com/p/82446482

 

1、Google Webrtc介绍

WebRTC（Web Real-Time Communication）实现了基于网页的视频会议，标准是WHATWG 协议，目的是通过浏览器提供简单的javascript就可以达到实时通讯（Real-Time Communications (RTC)）能力。

提供了视频会议的核心技术，包括音视频的采集、编解码、网络传输、显示等功能，并且还支持跨平台：windows，linux，mac，android，音视频通讯技术是基于p2p实现的

2、Google Webrtc服务器配置

信令服务器(signaling)，转发服务器(TURN)，穿透服务器(STUN)（自行百度，配置），更详细的介绍请看书籍 WebRtc权威指南

2.1 信令服务器(signaling)

WebRTC 之间使用PeerConnection交流数据，但还需要一种机制来协调沟通和发送控制消息，这一过程称之为信令传输

2.2 转发服务器(TURN) & 穿透服务器(STUN)

WebRTC 被设计为点对点工作模式，所以用户之间是尽可能地通过最短路线进行连接，然而在现实世界当中：客户端应用需要穿透 NAT 网关 和防火墙，并且点对点网络需要握手来防止直接连接失败，在这一过程中，WebRTC使用STUN服务器和TURN服务器来获取计算机IP地址来保证点对点连接成功

3、ICE框架

基于信令协议的多媒体传输是一个两段式传输，首先通过信令协议（如WebSocket）建立一个连接，通过该连接，双方交换传输媒体时所必须的信息。基于传输效率的考虑，在完成第一阶段的交互之后，通信双方会建立一条通道来实现媒体传输，以减少传输时延、降低丢包率并减少开销。由于使用新的链路，当传输双方有任意一方位于NAT之后，新的传输链路就需要考虑NAT穿越的问题了通常有四种形式的NAT，每一种NAT都有相应的解决方案，然而在复杂的网络环境中，由于每一种NAT穿越方案都局限于对应的NAT方式，这些方案就给整个系统带来了一定的复杂性。在这种背景下，交互式连通建立方式(Interactive Connectivity Establishment)即ICE解决方案应运而生，ICE能够在不增加整个系统的复杂性和脆弱性的情况下，实现对各种形式的NAT的穿越。

官方提供的实现原理 基于下图

 

4、Android Webrtc的配置

客户端和服务端通信 采用WebSocket
摄像头，录音，SD卡读取等其他权限加入，有些需要在运行时调用

4.1 在build.gradle 引入websocket 和 webrtc

    dependencies {
            implementation 'org.webrtc:google-webrtc:1.0.28513'
            implementation 'org.java-websocket:Java-WebSocket:1.4.0'
            implementation 'com.google.code.gson:gson:2.8.5'
        }

5、Android Webrtc的使用

5.1 创建websocket

     private void connectionWebsocket() {
            try {
                webSocketClient = new WebSocketClient(URI.create(Constant.URL)) {
                    @Override
                    public void onOpen(ServerHandshake handshakedata) {
                        setText("已连接");
                        Log.e(TAG, "onOpen == Status == " + handshakedata.getHttpStatus() + " StatusMessage == " + handshakedata.getHttpStatusMessage());
                        Model model = new Model(Constant.REGISTER, getFromName(), getFrom(), getToName(), getTo());
                        webSocketClient.send(new Gson().toJson(model));
                    }

                    @Override
                    public void onMessage(String message) {
                        Log.e(TAG, "onMessage == " + message);
                        if (!TextUtils.isEmpty(message)) {
                            Model model = new Gson().fromJson(message, Model.class);
                            if (model != null) {
                                String id = model.getId();
                                if (!TextUtils.isEmpty(id)) {
                                    int isSucceed = model.getIsSucceed();
                                    switch (id) {
                                        case Constant.REGISTER_RESPONSE:
                                            if (isSucceed == Constant.RESPONSE_SUCCEED) {
                                                Message msg = new Message();
                                                msg.obj = Constant.OPEN;
                                                handler.sendMessage(msg);
                                                Log.e(TAG, "连接成功");
                                            } else if (isSucceed == Constant.RESPONSE_FAILURE) {
                                                Log.e(TAG, "注册失败，已经注册");
                                            }
                                            break;
                                        case Constant.CALL_RESPONSE:
                                            if (isSucceed == Constant.RESPONSE_SUCCEED) {
                                                Log.e(TAG, "对方在线，创建sdp offer");
                                                createOffer();
                                            } else if (isSucceed == Constant.RESPONSE_FAILURE) {
                                                Log.e(TAG, "对方不在线，连接失败");
                                            }
                                            break;
                                        case Constant.INCALL:
                                            isIncall();
                                            break;
                                        case Constant.INCALL_RESPONSE:
                                            if (isSucceed == Constant.RESPONSE_SUCCEED) {
                                                createOffer();
                                                Log.e(TAG, "对方同意接听");
                                            } else if (isSucceed == Constant.RESPONSE_FAILURE) {
                                                Log.e(TAG, "对方拒绝接听");
                                            }
                                            break;
                                        case Constant.OFFER:
                                            //收到对方offer sdp
                                            SessionDescription sessionDescription1 = model.getSessionDescription();
                                            peerConnection.setRemoteDescription(observer, sessionDescription1);
                                            createAnswer();
                                            break;
                                        case Constant.CANDIDATE:
                                            //服务端 发送 接收方sdpAnswer
                                            IceCandidate iceCandidate = model.getIceCandidate();
                                            if (iceCandidate != null) {
                                                peerConnection.addIceCandidate(iceCandidate);
                                            }
                                            break;
                                    }
                                }
                            }
                        }
                    }

                    @Override
                    public void onClose(int code, String reason, boolean remote) {
                        setText("已关闭");
                        Log.e(TAG, "onClose == code " + code + " reason == " + reason + " remote == " + remote);
                    }

                    @Override
                    public void onError(Exception ex) {
                        setText("onError == " + ex.getMessage());
                        Log.e(TAG, "onError== " + ex.getMessage());
                    }
                };
                webSocketClient.connect();
            } catch (Exception e) {
                Log.d(TAG, "socket Exception : " + e.getMessage());
            }
        }

5.2 创建websocket成功后开始创建PeerConnection，穿透服务器采用Google提供的("stun:http://stun.l.google.com:19302")

    private void createPeerConnection() {
            //Initialising PeerConnectionFactory
            InitializationOptions initializationOptions = InitializationOptions.builder(this)
                    .setEnableInternalTracer(true)
                    .setFieldTrials("WebRTC-H264HighProfile/Enabled/")
                    .createInitializationOptions();
            PeerConnectionFactory.initialize(initializationOptions);
            //创建EglBase对象
            eglBase = EglBase.create();
            PeerConnectionFactory.Options options = new PeerConnectionFactory.Options();
            options.disableEncryption = true;
            options.disableNetworkMonitor = true;
            peerConnectionFactory = PeerConnectionFactory.builder()
                    .setVideoDecoderFactory(new DefaultVideoDecoderFactory(eglBase.getEglBaseContext()))
                    .setVideoEncoderFactory(new DefaultVideoEncoderFactory(eglBase.getEglBaseContext(), true, true))
                    .setOptions(options)
                    .createPeerConnectionFactory();
            // 配置STUN穿透服务器  转发服务器
            iceServers = new ArrayList<>();
            PeerConnection.IceServer iceServer = PeerConnection.IceServer.builder(Constant.STUN).createIceServer();
            iceServers.add(iceServer);

            streamList = new ArrayList<>();

            PeerConnection.RTCConfiguration configuration = new PeerConnection.RTCConfiguration(iceServers);

            PeerConnectionObserver connectionObserver = getObserver();
            peerConnection = peerConnectionFactory.createPeerConnection(configuration, connectionObserver);


            /*
            DataChannel.Init 可配参数说明：
            ordered：是否保证顺序传输；
            maxRetransmitTimeMs：重传允许的最长时间；
            maxRetransmits：重传允许的最大次数；
            */
            DataChannel.Init init = new DataChannel.Init();
            if (peerConnection != null) {
                channel = peerConnection.createDataChannel(Constant.CHANNEL, init);
            }
            DateChannelObserver channelObserver = new DateChannelObserver();
            connectionObserver.setObserver(channelObserver);
            initView();
            initObserver();
        }

 

• 5.2.1 初始化view

    private void initSurfaceview(SurfaceViewRenderer localSurfaceView) {
            localSurfaceView.init(eglBase.getEglBaseContext(), null);
            localSurfaceView.setMirror(true);
            localSurfaceView.setScalingType(RendererCommon.ScalingType.SCALE_ASPECT_FILL);
            localSurfaceView.setKeepScreenOn(true);
            localSurfaceView.setZOrderMediaOverlay(true);
            localSurfaceView.setEnableHardwareScaler(false);
    }

• 5.2.2 初始化音频和视频

    /**
     * 创建本地视频
     *
     * @param localSurfaceView
     */
    private void startLocalVideoCapture(SurfaceViewRenderer localSurfaceView) {
        VideoSource videoSource = peerConnectionFactory.createVideoSource(true);
        SurfaceTextureHelper surfaceTextureHelper = SurfaceTextureHelper.create(Thread.currentThread().getName(), eglBase.getEglBaseContext());
        VideoCapturer videoCapturer = createVideoCapturer();
        videoCapturer.initialize(surfaceTextureHelper, this, videoSource.getCapturerObserver());
        videoCapturer.startCapture(Constant.VIDEO_RESOLUTION_WIDTH, Constant.VIDEO_RESOLUTION_HEIGHT, Constant.VIDEO_FPS); // width, height, frame per second
        videoTrack = peerConnectionFactory.createVideoTrack(Constant.VIDEO_TRACK_ID, videoSource);
        videoTrack.addSink(localSurfaceView);
        MediaStream localMediaStream = peerConnectionFactory.createLocalMediaStream(Constant.LOCAL_VIDEO_STREAM);
        localMediaStream.addTrack(videoTrack);
        peerConnection.addTrack(videoTrack, streamList);
        peerConnection.addStream(localMediaStream);
    }

    /**
     * 创建本地音频
     */
    private void startLocalAudioCapture() {
        //语音
        MediaConstraints audioConstraints = new MediaConstraints();
        //回声消除
        audioConstraints.mandatory.add(new MediaConstraints.KeyValuePair("googEchoCancellation", "true"));
        //自动增益
        audioConstraints.mandatory.add(new MediaConstraints.KeyValuePair("googAutoGainControl", "true"));
        //高音过滤
        audioConstraints.mandatory.add(new MediaConstraints.KeyValuePair("googHighpassFilter", "true"));
        //噪音处理
        audioConstraints.mandatory.add(new MediaConstraints.KeyValuePair("googNoiseSuppression", "true"));
        AudioSource audioSource = peerConnectionFactory.createAudioSource(audioConstraints);
        audioTrack = peerConnectionFactory.createAudioTrack(Constant.AUDIO_TRACK_ID, audioSource);
        MediaStream localMediaStream = peerConnectionFactory.createLocalMediaStream(Constant.LOCAL_AUDIO_STREAM);
        localMediaStream.addTrack(audioTrack);
        audioTrack.setVolume(Constant.VOLUME);
        peerConnection.addTrack(audioTrack, streamList);
        peerConnection.addStream(localMediaStream);
    }

5.3 创建PeerConnection成功后通过信令传输交换各自信息，实现视频通话，调整后的流程如下图

信令

    public static final String REGISTER = "register";//注册
    public static final String REGISTER_RESPONSE = "register_response";//注册回复
    public static final int RESPONSE_SUCCEED = 1;//1成功
    public static final int RESPONSE_FAILURE = 2;//2失败
    public static final String CALL = "call";//拨打
    public static final String CALL_RESPONSE = "call_response";//拨打回复
    public static final String INCALL = "incall";//接听
    public static final String INCALL_RESPONSE = "incall_response";//接听回复
    public static final String OFFER = "offer";//发送sdp信息
    public static final String CANDIDATE = "candidate";//ice互传

流程内容： 客户端A，客户端B

• 5.3.1 -->> A 和 B 都注册成功后，A 发起 call，服务端收到A的指令后转发给B， B接受后发给服务器，服务器转发给A
• 5.3.2 -->> A createOffer 将自己的SessionDescription 发给服务器，服务器转发给B
• 5.3.3 -->> B 收到后将A的SessionDescription 设置到自己的setRemoteDescription，同时createAnswer 发给服务器，服务器在转发A
• 5.3.4 -->> A 收到后将B的SessionDescription 设置到自己的setRemoteDescription
• 5.3.5 -->> A 在PeerConnectionObserver 的 onIceCandidate方法中，将收到的IceCandidate 发给服务端，服务器转发给B
• 5.3.6 -->> B 收到后在将IceCandidate 设置到自己的addIceCandidate
• 5.3.7 -->> B 在PeerConnectionObserver 的 onIceCandidate方法中，将收到的IceCandidate 发给服务端，服务器转发给A
• 5.3.8 -->> A 收到后在将IceCandidate 设置到自己的addIceCandidate
• 5.3.9 -->> A 和 B 在PeerConnectionObserver 的 onAddStream方法中，将远端的流媒体加入到本地的View
• 5.3.10 -->> 交互已经结束，可以正常视频通话

详细的流程，json 格式

       isSucceed 1成功 2失败
	
	"from": "11",  "fromName": "王安", "to": "12", "toName": "往事"
		
	1.注册 
	from 发送服务端：register 
	{
	"from": "11",
	"fromName": "王安",
	"id": "register",
	"isSucceed": 0
	}
	
	from接收：register_response 
	{
	"id": "register_response",
	"isSucceed": 1
	}
	
	2.呼叫
	from 发送服务端：call 
	{
	"from": "11",
	"fromName": "王安",
	"id": "call",
	"isSucceed": 0,
	"to": "12",
	"toName": "往事"
	}
	
	2.1服务端做判断
	
	如果不在线 直接返回 "isSucceed": 1
	{
	"id": "call_response",
	"isSucceed": 1
	}
	 
	在线 返回给to做判断
	
	to 接收：incall 
	改变本地状态
	{
	"id": "incall",
	"isSucceed": 0
	}
		to 发送服务端 拒绝："isSucceed": 2
		{
			"from": "12",
			"fromName": "往事",
			"id": "incall",
			"isSucceed": 2,
			"to": "11",
			"toName": "王安"
		}
			from接收：incall_response
			做拒绝的操作
			{
				"id": "incall_response",
				"from": "12",
				"fromName": "往事",
				"to": "11",
				"toName": "王安",
				"isSucceed": 2
			}
			
	-------------------------------------------------
		
		to 发送服务端 同意："isSucceed": 1
		{
			"from": "12",
			"fromName": "往事",
			"id": "incall",
			"isSucceed": 1,
			"to": "11",
			"toName": "王安"
		}
			from接收 同意：incall_response
			  
			{
				"id": "incall_response",
				"from": "12",
				"fromName": "往事",
				"to": "11",
				"toName": "王安",
				"isSucceed": 1
			}
	
	3.to同意后 from发送流
	from 发送服务端：offer
	{
	"from": "11",
	"fromName": "王安",
	"id": "offer",
	"isSucceed": 0,
	"sessionDescription": {
	"description": "v=0\r\no=- 3285195603599485281 2 IN IP4 127.0.0.1\r\ns=-\r\nt=0 0\r\na=group:BUNDLE video\r\na=msid-semantic: WMS localstream\r\nm=video 9 RTP/AVPF 96 97 98 99 100 101 127 124 125\r\nc=IN IP4 0.0.0.0\r\na=rtcp:9 IN IP4 0.0.0.0\r\na=ice-ufrag:9Jqg\r\na=ice-pwd:lM34EvVxjaPGBislEH9VccVu\r\na=ice-options:trickle renomination\r\na=mid:video\r\na=extmap:14 urn:ietf:params:rtp-hdrext:toffset\r\na=extmap:13 http://www.webrtc.org/experiments/rtp-hdrext/abs-send-time\r\na=extmap:3 urn:3gpp:video-orientation\r\na=extmap:2 http://www.ietf.org/id/draft-holmer-rmcat-transport-wide-cc-extensions-01\r\na=extmap:5 http://www.webrtc.org/experiments/rtp-hdrext/playout-delay\r\na=extmap:6 http://www.webrtc.org/experiments/rtp-hdrext/video-content-type\r\na=extmap:7 http://www.webrtc.org/experiments/rtp-hdrext/video-timing\r\na=extmap:8 http://tools.ietf.org/html/draft-ietf-avtext-framemarking-07\r\na=extmap:9 http://www.webrtc.org/experiments/rtp-hdrext/color-space\r\na=sendrecv\r\na=rtcp-mux\r\na=rtcp-rsize\r\na=rtpmap:96 VP8/90000\r\na=rtcp-fb:96 goog-remb\r\na=rtcp-fb:96 transport-cc\r\na=rtcp-fb:96 ccm fir\r\na=rtcp-fb:96 nack\r\na=rtcp-fb:96 nack pli\r\na=rtpmap:97 rtx/90000\r\na=fmtp:97 apt=96\r\na=rtpmap:98 VP9/90000\r\na=rtcp-fb:98 goog-remb\r\na=rtcp-fb:98 transport-cc\r\na=rtcp-fb:98 ccm fir\r\na=rtcp-fb:98 nack\r\na=rtcp-fb:98 nack pli\r\na=rtpmap:99 rtx/90000\r\na=fmtp:99 apt=98\r\na=rtpmap:100 H264/90000\r\na=rtcp-fb:100 goog-remb\r\na=rtcp-fb:100 transport-cc\r\na=rtcp-fb:100 ccm fir\r\na=rtcp-fb:100 nack\r\na=rtcp-fb:100 nack pli\r\na=fmtp:100 level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=42e01f\r\na=rtpmap:101 rtx/90000\r\na=fmtp:101 apt=100\r\na=rtpmap:127 red/90000\r\na=rtpmap:124 rtx/90000\r\na=fmtp:124 apt=127\r\na=rtpmap:125 ulpfec/90000\r\na=ssrc-group:FID 1791802911 305163890\r\na=ssrc:1791802911 cname:8uTWIc2YbUNSY02u\r\na=ssrc:1791802911 msid:localstream videtrack\r\na=ssrc:1791802911 mslabel:localstream\r\na=ssrc:1791802911 label:videtrack\r\na=ssrc:305163890 cname:8uTWIc2YbUNSY02u\r\na=ssrc:305163890 msid:localstream videtrack\r\na=ssrc:305163890 mslabel:localstream\r\na=ssrc:305163890 label:videtrack\r\n",
	"type": "OFFER"
	},
	"to": "12",
	"toName": "往事"
	}
	
	to接收：offer
	{
	"id": "offer",
	"from": "11",
	"fromName": "王安",
	"to": "12",
	"toName": "往事",
	"sessionDescription": {
	"type": "OFFER",
	"description": "v=0\r\no=- 3285195603599485281 2 IN IP4 127.0.0.1\r\ns=-\r\nt=0 0\r\na=group:BUNDLE video\r\na=msid-semantic: WMS localstream\r\nm=video 9 RTP/AVPF 96 97 98 99 100 101 127 124 125\r\nc=IN IP4 0.0.0.0\r\na=rtcp:9 IN IP4 0.0.0.0\r\na=ice-ufrag:9Jqg\r\na=ice-pwd:lM34EvVxjaPGBislEH9VccVu\r\na=ice-options:trickle renomination\r\na=mid:video\r\na=extmap:14 urn:ietf:params:rtp-hdrext:toffset\r\na=extmap:13 http://www.webrtc.org/experiments/rtp-hdrext/abs-send-time\r\na=extmap:3 urn:3gpp:video-orientation\r\na=extmap:2 http://www.ietf.org/id/draft-holmer-rmcat-transport-wide-cc-extensions-01\r\na=extmap:5 http://www.webrtc.org/experiments/rtp-hdrext/playout-delay\r\na=extmap:6 http://www.webrtc.org/experiments/rtp-hdrext/video-content-type\r\na=extmap:7 http://www.webrtc.org/experiments/rtp-hdrext/video-timing\r\na=extmap:8 http://tools.ietf.org/html/draft-ietf-avtext-framemarking-07\r\na=extmap:9 http://www.webrtc.org/experiments/rtp-hdrext/color-space\r\na=sendrecv\r\na=rtcp-mux\r\na=rtcp-rsize\r\na=rtpmap:96 VP8/90000\r\na=rtcp-fb:96 goog-remb\r\na=rtcp-fb:96 transport-cc\r\na=rtcp-fb:96 ccm fir\r\na=rtcp-fb:96 nack\r\na=rtcp-fb:96 nack pli\r\na=rtpmap:97 rtx/90000\r\na=fmtp:97 apt=96\r\na=rtpmap:98 VP9/90000\r\na=rtcp-fb:98 goog-remb\r\na=rtcp-fb:98 transport-cc\r\na=rtcp-fb:98 ccm fir\r\na=rtcp-fb:98 nack\r\na=rtcp-fb:98 nack pli\r\na=rtpmap:99 rtx/90000\r\na=fmtp:99 apt=98\r\na=rtpmap:100 H264/90000\r\na=rtcp-fb:100 goog-remb\r\na=rtcp-fb:100 transport-cc\r\na=rtcp-fb:100 ccm fir\r\na=rtcp-fb:100 nack\r\na=rtcp-fb:100 nack pli\r\na=fmtp:100 level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=42e01f\r\na=rtpmap:101 rtx/90000\r\na=fmtp:101 apt=100\r\na=rtpmap:127 red/90000\r\na=rtpmap:124 rtx/90000\r\na=fmtp:124 apt=127\r\na=rtpmap:125 ulpfec/90000\r\na=ssrc-group:FID 1791802911 305163890\r\na=ssrc:1791802911 cname:8uTWIc2YbUNSY02u\r\na=ssrc:1791802911 msid:localstream videtrack\r\na=ssrc:1791802911 mslabel:localstream\r\na=ssrc:1791802911 label:videtrack\r\na=ssrc:305163890 cname:8uTWIc2YbUNSY02u\r\na=ssrc:305163890 msid:localstream videtrack\r\na=ssrc:305163890 mslabel:localstream\r\na=ssrc:305163890 label:videtrack\r\n"
	},
	"isSucceed": 0
	}
	
	to接收到 offer 创建answer 创建完 to 发送服务端：offer
	{
	"from": "12",
	"fromName": "往事",
	"id": "offer",
	"isSucceed": 0,
	"sessionDescription": {
	"description": "v=0\r\no=- 8665372075017263288 2 IN IP4 127.0.0.1\r\ns=-\r\nt=0 0\r\na=group:BUNDLE video\r\na=msid-semantic: WMS localstream\r\nm=video 9 RTP/AVPF 96 97 98 99 100 101 127 124 125\r\nc=IN IP4 0.0.0.0\r\na=rtcp:9 IN IP4 0.0.0.0\r\na=ice-ufrag:zoQn\r\na=ice-pwd:oBePBH1X7SehiT6Tb83SZV2U\r\na=ice-options:trickle renomination\r\na=mid:video\r\na=extmap:14 urn:ietf:params:rtp-hdrext:toffset\r\na=extmap:13 http://www.webrtc.org/experiments/rtp-hdrext/abs-send-time\r\na=extmap:3 urn:3gpp:video-orientation\r\na=extmap:2 http://www.ietf.org/id/draft-holmer-rmcat-transport-wide-cc-extensions-01\r\na=extmap:5 http://www.webrtc.org/experiments/rtp-hdrext/playout-delay\r\na=extmap:6 http://www.webrtc.org/experiments/rtp-hdrext/video-content-type\r\na=extmap:7 http://www.webrtc.org/experiments/rtp-hdrext/video-timing\r\na=extmap:8 http://tools.ietf.org/html/draft-ietf-avtext-framemarking-07\r\na=extmap:9 http://www.webrtc.org/experiments/rtp-hdrext/color-space\r\na=sendrecv\r\na=rtcp-mux\r\na=rtcp-rsize\r\na=rtpmap:96 VP8/90000\r\na=rtcp-fb:96 goog-remb\r\na=rtcp-fb:96 transport-cc\r\na=rtcp-fb:96 ccm fir\r\na=rtcp-fb:96 nack\r\na=rtcp-fb:96 nack pli\r\na=rtpmap:97 rtx/90000\r\na=fmtp:97 apt=96\r\na=rtpmap:98 VP9/90000\r\na=rtcp-fb:98 goog-remb\r\na=rtcp-fb:98 transport-cc\r\na=rtcp-fb:98 ccm fir\r\na=rtcp-fb:98 nack\r\na=rtcp-fb:98 nack pli\r\na=rtpmap:99 rtx/90000\r\na=fmtp:99 apt=98\r\na=rtpmap:100 H264/90000\r\na=rtcp-fb:100 goog-remb\r\na=rtcp-fb:100 transport-cc\r\na=rtcp-fb:100 ccm fir\r\na=rtcp-fb:100 nack\r\na=rtcp-fb:100 nack pli\r\na=fmtp:100 level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=42e01f\r\na=rtpmap:101 rtx/90000\r\na=fmtp:101 apt=100\r\na=rtpmap:127 red/90000\r\na=rtpmap:124 rtx/90000\r\na=fmtp:124 apt=127\r\na=rtpmap:125 ulpfec/90000\r\na=ssrc-group:FID 330040035 1917181902\r\na=ssrc:330040035 cname:uxoKaX6C0J4LHdZ2\r\na=ssrc:330040035 msid:localstream videtrack\r\na=ssrc:330040035 mslabel:localstream\r\na=ssrc:330040035 label:videtrack\r\na=ssrc:1917181902 cname:uxoKaX6C0J4LHdZ2\r\na=ssrc:1917181902 msid:localstream videtrack\r\na=ssrc:1917181902 mslabel:localstream\r\na=ssrc:1917181902 label:videtrack\r\n",
	"type": "ANSWER"
	},
	"to": "11",
	"toName": "王安"
	}
	
	4.ice交换
	from 发送服务端：candidate
	{
	"from": "11",
	"fromName": "王安",
	"iceCandidate": {
	"sdp": "candidate:3575964346 1 udp 2122260223 192.168.0.166 47369 typ host generation 0 ufrag 9Jqg network-id 3 network-cost 10",
	"sdpMLineIndex": 0,
	"sdpMid": "video",
	"serverUrl": ""
	},
	"id": "candidate",
	"isSucceed": 0,
	"to": "12",
	"toName": "往事"
	}
	
	to 接收：candidate
	
	{
	"from": "11",
	"fromName": "王安",
	"iceCandidate": {
	"sdp": "candidate:3575964346 1 udp 2122260223 192.168.0.166 47369 typ host generation 0 ufrag 9Jqg network-id 3 network-cost 10",
	"sdpMLineIndex": 0,
	"sdpMid": "video",
	"serverUrl": ""
	},
	"id": "candidate",
	"isSucceed": 0,
	"to": "12",
	"toName": "往事"
	}
	
	to 发送服务端：candidate
	{
	"from": "12",
	"fromName": "往事",
	"iceCandidate": {
	"sdp": "candidate:559267639 1 udp 2122202367 ::1 55843 typ host generation 0 ufrag zoQn network-id 2",
	"sdpMLineIndex": 0,
	"sdpMid": "video",
	"serverUrl": ""
	},
	"id": "candidate",
	"isSucceed": 0,
	"to": "11",
	"toName": "王安"
	}
	
	from接收：candidate
	{
	"from": "12",
	"fromName": "往事",
	"iceCandidate": {
	"sdp": "candidate:559267639 1 udp 2122202367 ::1 55843 typ host generation 0 ufrag zoQn network-id 2",
	"sdpMLineIndex": 0,
	"sdpMid": "video",
	"serverUrl": ""
	},
	"id": "candidate",
	"isSucceed": 0,
	"to": "11",
	"toName": "王安"
	}

5.4 实现视频通话，部分截图