Masui Masanori

Posted on May 21, 2022

[Go] Try Pion/WebRTC with SSE

#go #pion #webrtc

Intro

This time, I will try Pion/WebRTC.

pion/webrtc - GitHub

Because Pion already has good examples, I will create a sample based on SFU-WebSocket of example-webrtc-applications.

example-webrtc-applications/sfu-ws - pion/example-webrtc-applications - GitHub

I will try changing these points.

Use SSE(Server-Sent Events) for signaling
Start connecting manually

I will add WebRTC functions into the last sample project.

[Go] Try Server-Sent Events

And I also refer this post(especially the client-side).

[ASP.NET Core][TypeScript] Try WebRTC

Environments

Go ver.go1.18.2 windows/amd64
Node.js ver.18.1.0

Connecting with WebRTC SFU

When I tried WebRTC last time, the server-side application just worked for signaling.
After signaling, the clients were directly connected to each other.

This time they will only connect to the server-side application.
After connecting, the clients will send video tracks and audio tracks to the server-side application.
And The server-side application send other clients' tracks as remote tracks to the clients.

Samples

This time, I publish the sample project on GitHub.

webappsample - GitHub

Client-side

Because the process for connecting starts from the server-side application.

So the client-side just needs handling offer and ICE candidate events.
And I will create a RTCPeerConnection on start.

main.page.ts



...

function handleReceivedMessage(value: string) {

    const message = JSON.parse(value);

    if(!checkIsClientMessage(message)) {

        return;

    }

    switch(message.event) {

        case "text":

            view.addReceivedText({ user: message.userName, message: message.data });

            break;

        case "offer":

            webrtc.handleOffer(JSON.parse(message.data));

            break;

        case "candidate":

            webrtc.handleCandidate(JSON.parse(message.data));

            break;

    }

}

function sendAnswer(data: RTCSessionDescriptionInit) {

    if(!hasAnyTexts(userName)) {

        return;

    }

    sse.sendMessage({userName, event: "answer", data: JSON.stringify(data)});

}

function sendCandidate(data: RTCIceCandidate) {

    if(!hasAnyTexts(userName)) {

        return;

    }

    sse.sendMessage({userName, event: "candidate", data: JSON.stringify(data)});

}

function checkIsClientMessage(value: any): value is ClientMessage {

    // All messages from the server-side application are sent as "ClientMessage".

    if(value == null) {

        return false;

    }

    if(("event" in value &&

        typeof value["event"] === "string") === false) {

        return false;

    }

    if(("data" in value &&

        typeof value["data"] === "string") === false) {

        return false;

    }

    return true;

}

init();

webrtc.controller.ts



export class WebRtcController {

    private webcamStream: MediaStream|null = null; 

    private peerConnection: RTCPeerConnection|null = null;

    private answerSentEvent: ((data: RTCSessionDescriptionInit) => void)|null = null;

    private candidateSentEvent: ((data: RTCIceCandidate) => void)|null = null;

    public init() {

        const localVideo = document.getElementById("local_video") as HTMLVideoElement;

        localVideo.addEventListener("canplay", () => {

            const width = 320;

            const height = localVideo.videoHeight / (localVideo.videoWidth/width);


            localVideo.setAttribute("width", width.toString());

            localVideo.setAttribute("height", height.toString());

          }, false);

        navigator.mediaDevices.getUserMedia({ video: true, audio: true })

          .then(stream => {

              localVideo.srcObject = stream;

              localVideo.play();

              this.webcamStream = stream;

              // create a RTCPeerConnection after getting local MediaStream

              this.connect();

          })

          .catch(err => console.error(An error occurred: </span><span class="p">${</span><span class="nx">err</span><span class="p">}</span><span class="s2">));

    }

...

    /** handle received offer and send answer /

    public handleOffer(data: RTCSessionDescription|null|undefined) {

        if(this.peerConnection == null ||

                data == null) {

            return;

        }

        this.peerConnection.setRemoteDescription(data);

        this.peerConnection.createAnswer()

            .then(answer => {

                if(this.peerConnection != null) {

                    this.peerConnection.setLocalDescription(answer);

                }

                if(this.answerSentEvent != null) {

                    this.answerSentEvent(answer);

                }

            });

    }

    /* add ICE Candidate */

    public handleCandidate(data: RTCIceCandidate|null|undefined) {

        if(this.peerConnection == null ||

            data == null) {

            return;

        }

        this.peerConnection.addIceCandidate(data);

    }

    private connect() {

        if(this.webcamStream == null) {

            return;

        }

        this.peerConnection = new RTCPeerConnection({

            iceServers: [{

                urls: stun:stun.l.google.com:19302,  // A STUN server              

            }]

        });

        // Add remote video tracks as new video elements.

        this.peerConnection.ontrack = (ev) => {

            if (ev.track.kind === "audio" ||

                ev.streams[0] == null) {

              return;

            }


            const remoteVideo = document.createElement("video");

            remoteVideo.srcObject = ev.streams[0];

            remoteVideo.autoplay = true;

            remoteVideo.controls = true;

            const videoArea = document.getElementById("remote_video_area") as HTMLElement;

            videoArea.appendChild(remoteVideo);

            ev.track.onmute = () => {

                remoteVideo.play();

            };

            ev.streams[0].onremovetrack = () => {

              if (remoteVideo.parentNode) {

                remoteVideo.parentNode.removeChild(remoteVideo);

              }

            };

          };

        this.webcamStream.getTracks().forEach(track => {

            if(this.peerConnection == null ||

                this.webcamStream == null) {

                return;

            }

            this.peerConnection.addTrack(track, this.webcamStream)

        });

        this.peerConnection.onicecandidate = ev => {

            if (ev.candidate == null ||

                this.candidateSentEvent == null) {

              return;

            }

            this.candidateSentEvent(ev.candidate);

        };

    }


}

Server-side

sseClient.go



package main

import (

    "encoding/json"

    "fmt"

    "io/ioutil"

    "log"

    "net/http"

<span class="s">"github.com/pion/webrtc/v3"</span>



    

    




)

type SSEClient struct {

    candidateFound        chan webrtc.ICECandidate

    changeConnectionState chan webrtc.PeerConnectionState

    addTrack              chan webrtc.TrackRemote

    userName              string

    w                     http.ResponseWriter

}

func newSSEClient(userName string, w http.ResponseWriter) SSEClient {

    return &SSEClient{

        candidateFound:        make(chan webrtc.ICECandidate),

        changeConnectionState: make(chan webrtc.PeerConnectionState),

        addTrack:              make(chan *webrtc.TrackRemote),

        userName:              userName,

        w:                     w,

    }

}

func registerSSEClient(w http.ResponseWriter, r http.Request, hub SSEHub) {

    userName, err := getParam(r, "user")

    if err != nil {

        log.Println(err.Error())

        fmt.Fprint(w, "The parameters have no names")

        return

    }

    newClient := newSSEClient(userName, w)

    ps, err := NewPeerConnectionState(newClient)

    if err != nil {

        log.Println(err.Error())

        fmt.Fprint(w, "Failed connection")

        return

    }

    w.Header().Set("Content-Type", "text/event-stream")

    w.Header().Set("Cache-Control", "no-cache")

    w.Header().Set("Connection", "keep-alive")

<span class="n">hub</span><span class="o">.</span><span class="n">register</span> <span class="o">&lt;-</span> <span class="n">ps</span>

<span class="c">// For pushing data to clients, I call "flusher.Flush()"</span>
<span class="n">flusher</span><span class="p">,</span> <span class="n">_</span> <span class="o">:=</span> <span class="n">w</span><span class="o">.</span><span class="p">(</span><span class="n">http</span><span class="o">.</span><span class="n">Flusher</span><span class="p">)</span>
<span class="k">defer</span> <span class="k">func</span><span class="p">()</span> <span class="p">{</span>
    <span class="n">hub</span><span class="o">.</span><span class="n">unregister</span> <span class="o">&lt;-</span> <span class="n">ps</span>
    <span class="k">if</span> <span class="n">ps</span><span class="o">.</span><span class="n">peerConnection</span><span class="o">.</span><span class="n">ConnectionState</span><span class="p">()</span> <span class="o">!=</span> <span class="n">webrtc</span><span class="o">.</span><span class="n">PeerConnectionStateClosed</span> <span class="p">{</span>
        <span class="n">ps</span><span class="o">.</span><span class="n">peerConnection</span><span class="o">.</span><span class="n">Close</span><span class="p">()</span>
    <span class="p">}</span>
    <span class="nb">close</span><span class="p">(</span><span class="n">newClient</span><span class="o">.</span><span class="n">candidateFound</span><span class="p">)</span>
    <span class="nb">close</span><span class="p">(</span><span class="n">newClient</span><span class="o">.</span><span class="n">changeConnectionState</span><span class="p">)</span>
    <span class="nb">close</span><span class="p">(</span><span class="n">newClient</span><span class="o">.</span><span class="n">addTrack</span><span class="p">)</span>
<span class="p">}()</span>
<span class="k">for</span> <span class="p">{</span>
    <span class="c">// handle PeerConnection events and close SSE event.</span>
    <span class="k">select</span> <span class="p">{</span>
    <span class="k">case</span> <span class="n">candidate</span> <span class="o">:=</span> <span class="o">&lt;-</span><span class="n">newClient</span><span class="o">.</span><span class="n">candidateFound</span><span class="o">:</span>
        <span class="n">jsonValue</span><span class="p">,</span> <span class="n">err</span> <span class="o">:=</span> <span class="n">NewCandidateMessageJSON</span><span class="p">(</span><span class="n">newClient</span><span class="o">.</span><span class="n">userName</span><span class="p">,</span> <span class="n">candidate</span><span class="p">)</span>
        <span class="k">if</span> <span class="n">err</span> <span class="o">!=</span> <span class="no">nil</span> <span class="p">{</span>
            <span class="n">log</span><span class="o">.</span><span class="n">Println</span><span class="p">(</span><span class="n">err</span><span class="o">.</span><span class="n">Error</span><span class="p">())</span>
            <span class="k">return</span>
        <span class="p">}</span>
        <span class="n">fmt</span><span class="o">.</span><span class="n">Fprintf</span><span class="p">(</span><span class="n">w</span><span class="p">,</span> <span class="s">"data: %s</span><span class="se">\n\n</span><span class="s">"</span><span class="p">,</span> <span class="n">jsonValue</span><span class="p">)</span>
        <span class="n">flusher</span><span class="o">.</span><span class="n">Flush</span><span class="p">()</span>
    <span class="k">case</span> <span class="n">track</span> <span class="o">:=</span> <span class="o">&lt;-</span><span class="n">newClient</span><span class="o">.</span><span class="n">addTrack</span><span class="o">:</span>
        <span class="n">hub</span><span class="o">.</span><span class="n">addTrack</span> <span class="o">&lt;-</span> <span class="n">track</span>
    <span class="k">case</span> <span class="n">connectionState</span> <span class="o">:=</span> <span class="o">&lt;-</span><span class="n">newClient</span><span class="o">.</span><span class="n">changeConnectionState</span><span class="o">:</span>
        <span class="k">switch</span> <span class="n">connectionState</span> <span class="p">{</span>
        <span class="k">case</span> <span class="n">webrtc</span><span class="o">.</span><span class="n">PeerConnectionStateFailed</span><span class="o">:</span>
            <span class="k">return</span>
        <span class="k">case</span> <span class="n">webrtc</span><span class="o">.</span><span class="n">PeerConnectionStateClosed</span><span class="o">:</span>
            <span class="k">return</span>
        <span class="p">}</span>
    <span class="k">case</span> <span class="o">&lt;-</span><span class="n">r</span><span class="o">.</span><span class="n">Context</span><span class="p">()</span><span class="o">.</span><span class="n">Done</span><span class="p">()</span><span class="o">:</span>
        <span class="c">// when "es.close()" is called, this loop operation will be ended.</span>
        <span class="k">return</span>
    <span class="p">}</span>
<span class="p">}</span>



    

    




}

func sendSSEMessage(w http.ResponseWriter, r http.Request, hub SSEHub) {

    w.Header().Set("Content-Type", "application/json")

    body, err := ioutil.ReadAll(r.Body)

<span class="k">if</span> <span class="n">err</span> <span class="o">!=</span> <span class="no">nil</span> <span class="p">{</span>
    <span class="n">log</span><span class="o">.</span><span class="n">Println</span><span class="p">(</span><span class="n">err</span><span class="o">.</span><span class="n">Error</span><span class="p">())</span>
    <span class="n">j</span><span class="p">,</span> <span class="n">_</span> <span class="o">:=</span> <span class="n">json</span><span class="o">.</span><span class="n">Marshal</span><span class="p">(</span><span class="n">GetFailed</span><span class="p">(</span><span class="s">"Failed reading values from body"</span><span class="p">))</span>
    <span class="n">w</span><span class="o">.</span><span class="n">Write</span><span class="p">(</span><span class="n">j</span><span class="p">)</span>
    <span class="k">return</span>
<span class="p">}</span>
<span class="n">message</span> <span class="o">:=</span> <span class="o">&amp;</span><span class="n">ClientMessage</span><span class="p">{}</span>
<span class="n">err</span> <span class="o">=</span> <span class="n">json</span><span class="o">.</span><span class="n">Unmarshal</span><span class="p">(</span><span class="n">body</span><span class="p">,</span> <span class="o">&amp;</span><span class="n">message</span><span class="p">)</span>
<span class="k">if</span> <span class="n">err</span> <span class="o">!=</span> <span class="no">nil</span> <span class="p">{</span>
    <span class="n">log</span><span class="o">.</span><span class="n">Println</span><span class="p">(</span><span class="n">err</span><span class="o">.</span><span class="n">Error</span><span class="p">())</span>
    <span class="n">j</span><span class="p">,</span> <span class="n">_</span> <span class="o">:=</span> <span class="n">json</span><span class="o">.</span><span class="n">Marshal</span><span class="p">(</span><span class="n">GetFailed</span><span class="p">(</span><span class="s">"Failed converting to ClientMessage"</span><span class="p">))</span>
    <span class="n">w</span><span class="o">.</span><span class="n">Write</span><span class="p">(</span><span class="n">j</span><span class="p">)</span>
    <span class="k">return</span>
<span class="p">}</span>
<span class="n">w</span><span class="o">.</span><span class="n">WriteHeader</span><span class="p">(</span><span class="m">200</span><span class="p">)</span>
<span class="n">hub</span><span class="o">.</span><span class="n">broadcast</span> <span class="o">&lt;-</span> <span class="o">*</span><span class="n">message</span>
<span class="n">data</span><span class="p">,</span> <span class="n">_</span> <span class="o">:=</span> <span class="n">json</span><span class="o">.</span><span class="n">Marshal</span><span class="p">(</span><span class="n">GetSucceeded</span><span class="p">())</span>
<span class="n">w</span><span class="o">.</span><span class="n">Write</span><span class="p">(</span><span class="n">data</span><span class="p">)</span>



    

    




}

peerConnectionState.go



package main

import (

    "github.com/pion/webrtc/v3"

)

type PeerConnectionState struct {

    peerConnection webrtc.PeerConnection

    client         SSEClient

}

func NewPeerConnectionState(client SSEClient) (PeerConnectionState, error) {

    peerConnection, err := webrtc.NewPeerConnection(webrtc.Configuration{

        ICEServers: []webrtc.ICEServer{

            {

                URLs: []string{

                    "stun:stun.l.google.com:19302",

                },

            },

        },

    })

    if err != nil {

        return nil, err

    }

    for , typ := range []webrtc.RTPCodecType{webrtc.RTPCodecTypeVideo, webrtc.RTPCodecTypeAudio} {

        if , err := peerConnection.AddTransceiverFromKind(typ, webrtc.RTPTransceiverInit{

            Direction: webrtc.RTPTransceiverDirectionRecvonly,

        }); err != nil {

            return nil, err

        }

    }

    // Add event handlers.

    peerConnection.OnICECandidate(func(i webrtc.ICECandidate) {

        if i == nil {

            return

        }

        client.candidateFound <- i

    })

    peerConnection.OnConnectionStateChange(func(p webrtc.PeerConnectionState) {

        // avoid panic after closing channel

        if p == webrtc.PeerConnectionStateClosed {

            _, ok := <-client.changeConnectionState

            if ok {

                client.changeConnectionState <- p

            }

            return

        }

        client.changeConnectionState <- p

    })

    peerConnection.OnTrack(func(t webrtc.TrackRemote, _ *webrtc.RTPReceiver) {

        client.addTrack <- t

    })

<span class="k">return</span> <span class="o">&amp;</span><span class="n">PeerConnectionState</span><span class="p">{</span>
    <span class="n">peerConnection</span><span class="o">:</span> <span class="n">peerConnection</span><span class="p">,</span>
    <span class="n">client</span><span class="o">:</span>         <span class="n">client</span><span class="p">,</span>
<span class="p">},</span> <span class="no">nil</span>



    

    




}

sseHub.go



package main

import (

    "encoding/json"

    "fmt"

    "log"

    "net/http"

    "time"

<span class="s">"github.com/pion/rtcp"</span>
<span class="s">"github.com/pion/webrtc/v3"</span>



    

    




)

type SSEHub struct {

    clients     map[PeerConnectionState]bool

    broadcast   chan ClientMessage

    register    chan PeerConnectionState

    unregister  chan PeerConnectionState

    trackLocals map[string]webrtc.TrackLocalStaticRTP

    addTrack    chan *webrtc.TrackRemote

}

func newSSEHub() SSEHub {

    return &SSEHub{

        clients:     make(map[PeerConnectionState]bool),

        broadcast:   make(chan ClientMessage),

        register:    make(chan PeerConnectionState),

        unregister:  make(chan PeerConnectionState),

        trackLocals: map[string]webrtc.TrackLocalStaticRTP{},

        addTrack:    make(chan webrtc.TrackRemote),

    }

}

func (h SSEHub) run() {

    go func() {

        for range time.NewTicker(time.Second  3).C {

            dispatchKeyFrame(h)

        }

    }()

    for {

        select {

        case client := <-h.register:

            h.clients[client] = true

            signalPeerConnections(h)

        case client := <-h.unregister:

            if _, ok := h.clients[client]; ok {

                delete(h.clients, client)

                signalPeerConnections(h)

            }

        case track := <-h.addTrack:

            trackLocal, err := webrtc.NewTrackLocalStaticRTP(track.Codec().RTPCodecCapability,

                track.ID(), track.StreamID())

            if err != nil {

                log.Println(err.Error())

                return

            }

            h.trackLocals[track.ID()] = trackLocal

            signalPeerConnections(h)

            go updateTrackValue(h, track)

    <span class="k">case</span> <span class="n">message</span> <span class="o">:=</span> <span class="o">&lt;-</span><span class="n">h</span><span class="o">.</span><span class="n">broadcast</span><span class="o">:</span>
        <span class="n">handleReceivedMessage</span><span class="p">(</span><span class="n">h</span><span class="p">,</span> <span class="n">message</span><span class="p">)</span>
    <span class="p">}</span>
<span class="p">}</span>



    

    




}

func updateTrackValue(h SSEHub, track webrtc.TrackRemote) {

    defer func() {

        delete(h.trackLocals, track.ID())

        signalPeerConnections(h)

    }()

<span class="n">buf</span> <span class="o">:=</span> <span class="nb">make</span><span class="p">([]</span><span class="kt">byte</span><span class="p">,</span> <span class="m">1500</span><span class="p">)</span>

<span class="k">for</span> <span class="p">{</span>
    <span class="n">i</span><span class="p">,</span> <span class="n">_</span><span class="p">,</span> <span class="n">err</span> <span class="o">:=</span> <span class="n">track</span><span class="o">.</span><span class="n">Read</span><span class="p">(</span><span class="n">buf</span><span class="p">)</span>
    <span class="k">if</span> <span class="n">err</span> <span class="o">!=</span> <span class="no">nil</span> <span class="p">{</span>
        <span class="k">return</span>
    <span class="p">}</span>
    <span class="k">if</span> <span class="n">_</span><span class="p">,</span> <span class="n">err</span> <span class="o">=</span> <span class="n">h</span><span class="o">.</span><span class="n">trackLocals</span><span class="p">[</span><span class="n">track</span><span class="o">.</span><span class="n">ID</span><span class="p">()]</span><span class="o">.</span><span class="n">Write</span><span class="p">(</span><span class="n">buf</span><span class="p">[</span><span class="o">:</span><span class="n">i</span><span class="p">]);</span> <span class="n">err</span> <span class="o">!=</span> <span class="no">nil</span> <span class="p">{</span>
        <span class="k">return</span>
    <span class="p">}</span>
<span class="p">}</span>



    

    




}

func handleReceivedMessage(h *SSEHub, message ClientMessage) {

    switch message.Event {

    case TextEvent:

        m, _ := json.Marshal(message)

        jsonText := string(m)

    <span class="k">for</span> <span class="n">client</span> <span class="o">:=</span> <span class="k">range</span> <span class="n">h</span><span class="o">.</span><span class="n">clients</span> <span class="p">{</span>
        <span class="n">flusher</span><span class="p">,</span> <span class="n">_</span> <span class="o">:=</span> <span class="n">client</span><span class="o">.</span><span class="n">client</span><span class="o">.</span><span class="n">w</span><span class="o">.</span><span class="p">(</span><span class="n">http</span><span class="o">.</span><span class="n">Flusher</span><span class="p">)</span>

        <span class="n">fmt</span><span class="o">.</span><span class="n">Fprintf</span><span class="p">(</span><span class="n">client</span><span class="o">.</span><span class="n">client</span><span class="o">.</span><span class="n">w</span><span class="p">,</span> <span class="s">"data: %s</span><span class="se">\n\n</span><span class="s">"</span><span class="p">,</span> <span class="n">jsonText</span><span class="p">)</span>
        <span class="n">flusher</span><span class="o">.</span><span class="n">Flush</span><span class="p">()</span>
    <span class="p">}</span>
<span class="k">case</span> <span class="n">CandidateEvent</span><span class="o">:</span>
    <span class="n">candidate</span> <span class="o">:=</span> <span class="n">webrtc</span><span class="o">.</span><span class="n">ICECandidateInit</span><span class="p">{}</span>
    <span class="k">if</span> <span class="n">err</span> <span class="o">:=</span> <span class="n">json</span><span class="o">.</span><span class="n">Unmarshal</span><span class="p">([]</span><span class="kt">byte</span><span class="p">(</span><span class="n">message</span><span class="o">.</span><span class="n">Data</span><span class="p">),</span> <span class="o">&amp;</span><span class="n">candidate</span><span class="p">);</span> <span class="n">err</span> <span class="o">!=</span> <span class="no">nil</span> <span class="p">{</span>
        <span class="n">log</span><span class="o">.</span><span class="n">Println</span><span class="p">(</span><span class="n">err</span><span class="p">)</span>
        <span class="k">return</span>
    <span class="p">}</span>
    <span class="k">for</span> <span class="n">pc</span> <span class="o">:=</span> <span class="k">range</span> <span class="n">h</span><span class="o">.</span><span class="n">clients</span> <span class="p">{</span>
        <span class="k">if</span> <span class="n">pc</span><span class="o">.</span><span class="n">client</span><span class="o">.</span><span class="n">userName</span> <span class="o">==</span> <span class="n">message</span><span class="o">.</span><span class="n">UserName</span> <span class="p">{</span>
            <span class="k">if</span> <span class="n">err</span> <span class="o">:=</span> <span class="n">pc</span><span class="o">.</span><span class="n">peerConnection</span><span class="o">.</span><span class="n">AddICECandidate</span><span class="p">(</span><span class="n">candidate</span><span class="p">);</span> <span class="n">err</span> <span class="o">!=</span> <span class="no">nil</span> <span class="p">{</span>
                <span class="n">log</span><span class="o">.</span><span class="n">Println</span><span class="p">(</span><span class="n">err</span><span class="p">)</span>
                <span class="k">return</span>
            <span class="p">}</span>
        <span class="p">}</span>
    <span class="p">}</span>
<span class="k">case</span> <span class="n">AnswerEvent</span><span class="o">:</span>
    <span class="n">answer</span> <span class="o">:=</span> <span class="n">webrtc</span><span class="o">.</span><span class="n">SessionDescription</span><span class="p">{}</span>
    <span class="k">if</span> <span class="n">err</span> <span class="o">:=</span> <span class="n">json</span><span class="o">.</span><span class="n">Unmarshal</span><span class="p">([]</span><span class="kt">byte</span><span class="p">(</span><span class="n">message</span><span class="o">.</span><span class="n">Data</span><span class="p">),</span> <span class="o">&amp;</span><span class="n">answer</span><span class="p">);</span> <span class="n">err</span> <span class="o">!=</span> <span class="no">nil</span> <span class="p">{</span>
        <span class="n">log</span><span class="o">.</span><span class="n">Println</span><span class="p">(</span><span class="n">err</span><span class="p">)</span>
        <span class="k">return</span>
    <span class="p">}</span>
    <span class="k">for</span> <span class="n">pc</span> <span class="o">:=</span> <span class="k">range</span> <span class="n">h</span><span class="o">.</span><span class="n">clients</span> <span class="p">{</span>
        <span class="k">if</span> <span class="n">pc</span><span class="o">.</span><span class="n">client</span><span class="o">.</span><span class="n">userName</span> <span class="o">==</span> <span class="n">message</span><span class="o">.</span><span class="n">UserName</span> <span class="p">{</span>
            <span class="k">if</span> <span class="n">err</span> <span class="o">:=</span> <span class="n">pc</span><span class="o">.</span><span class="n">peerConnection</span><span class="o">.</span><span class="n">SetRemoteDescription</span><span class="p">(</span><span class="n">answer</span><span class="p">);</span> <span class="n">err</span> <span class="o">!=</span> <span class="no">nil</span> <span class="p">{</span>
                <span class="n">log</span><span class="o">.</span><span class="n">Println</span><span class="p">(</span><span class="n">err</span><span class="p">)</span>
                <span class="k">return</span>
            <span class="p">}</span>
        <span class="p">}</span>
    <span class="p">}</span>

<span class="p">}</span>



    

    




}

func signalPeerConnections(h SSEHub) {

    defer func() {

        dispatchKeyFrame(h)

    }()

    for syncAttempt := 0; ; syncAttempt++ {

        if syncAttempt == 25 {

            // Release the lock and attempt a sync in 3 seconds. We might be blocking a RemoveTrack or AddTrack

            go func() {

                time.Sleep(time.Second  3)

                signalPeerConnections(h)

            }()

            return

        }

        // For ignoring errors like below, execute attemptSync multiple times.

        // InvalidModificationError: invalid proposed signaling state transition: have-local-offer->SetLocal(offer)->have-local-offer

        if !attemptSync(h) {

            break

        }

    }

}

// Share received tracks to all connected peers.

func attemptSync(h *SSEHub) bool {

    for ps := range h.clients {

        if ps.peerConnection.ConnectionState() == webrtc.PeerConnectionStateClosed {

            delete(h.clients, ps)

            // We modified the slice, start from the beginning

            return true

        }

        existingSenders := map[string]bool{}

    <span class="k">for</span> <span class="n">_</span><span class="p">,</span> <span class="n">sender</span> <span class="o">:=</span> <span class="k">range</span> <span class="n">ps</span><span class="o">.</span><span class="n">peerConnection</span><span class="o">.</span><span class="n">GetSenders</span><span class="p">()</span> <span class="p">{</span>
        <span class="k">if</span> <span class="n">sender</span><span class="o">.</span><span class="n">Track</span><span class="p">()</span> <span class="o">==</span> <span class="no">nil</span> <span class="p">{</span>
            <span class="k">continue</span>
        <span class="p">}</span>
        <span class="n">existingSenders</span><span class="p">[</span><span class="n">sender</span><span class="o">.</span><span class="n">Track</span><span class="p">()</span><span class="o">.</span><span class="n">ID</span><span class="p">()]</span> <span class="o">=</span> <span class="no">true</span>

        <span class="k">if</span> <span class="n">_</span><span class="p">,</span> <span class="n">ok</span> <span class="o">:=</span> <span class="n">h</span><span class="o">.</span><span class="n">trackLocals</span><span class="p">[</span><span class="n">sender</span><span class="o">.</span><span class="n">Track</span><span class="p">()</span><span class="o">.</span><span class="n">ID</span><span class="p">()];</span> <span class="o">!</span><span class="n">ok</span> <span class="p">{</span>
            <span class="k">if</span> <span class="n">err</span> <span class="o">:=</span> <span class="n">ps</span><span class="o">.</span><span class="n">peerConnection</span><span class="o">.</span><span class="n">RemoveTrack</span><span class="p">(</span><span class="n">sender</span><span class="p">);</span> <span class="n">err</span> <span class="o">!=</span> <span class="no">nil</span> <span class="p">{</span>
                <span class="k">return</span> <span class="no">true</span>
            <span class="p">}</span>
        <span class="p">}</span>
    <span class="p">}</span>
    <span class="k">for</span> <span class="n">_</span><span class="p">,</span> <span class="n">receiver</span> <span class="o">:=</span> <span class="k">range</span> <span class="n">ps</span><span class="o">.</span><span class="n">peerConnection</span><span class="o">.</span><span class="n">GetReceivers</span><span class="p">()</span> <span class="p">{</span>
        <span class="k">if</span> <span class="n">receiver</span><span class="o">.</span><span class="n">Track</span><span class="p">()</span> <span class="o">==</span> <span class="no">nil</span> <span class="p">{</span>
            <span class="k">continue</span>
        <span class="p">}</span>
        <span class="n">existingSenders</span><span class="p">[</span><span class="n">receiver</span><span class="o">.</span><span class="n">Track</span><span class="p">()</span><span class="o">.</span><span class="n">ID</span><span class="p">()]</span> <span class="o">=</span> <span class="no">true</span>
    <span class="p">}</span>
    <span class="k">for</span> <span class="n">trackID</span> <span class="o">:=</span> <span class="k">range</span> <span class="n">h</span><span class="o">.</span><span class="n">trackLocals</span> <span class="p">{</span>
        <span class="k">if</span> <span class="n">_</span><span class="p">,</span> <span class="n">ok</span> <span class="o">:=</span> <span class="n">existingSenders</span><span class="p">[</span><span class="n">trackID</span><span class="p">];</span> <span class="o">!</span><span class="n">ok</span> <span class="p">{</span>
            <span class="k">if</span> <span class="n">_</span><span class="p">,</span> <span class="n">err</span> <span class="o">:=</span> <span class="n">ps</span><span class="o">.</span><span class="n">peerConnection</span><span class="o">.</span><span class="n">AddTrack</span><span class="p">(</span><span class="n">h</span><span class="o">.</span><span class="n">trackLocals</span><span class="p">[</span><span class="n">trackID</span><span class="p">]);</span> <span class="n">err</span> <span class="o">!=</span> <span class="no">nil</span> <span class="p">{</span>
                <span class="k">return</span> <span class="no">true</span>
            <span class="p">}</span>
        <span class="p">}</span>
    <span class="p">}</span>

    <span class="n">offer</span><span class="p">,</span> <span class="n">err</span> <span class="o">:=</span> <span class="n">ps</span><span class="o">.</span><span class="n">peerConnection</span><span class="o">.</span><span class="n">CreateOffer</span><span class="p">(</span><span class="no">nil</span><span class="p">)</span>
    <span class="k">if</span> <span class="n">err</span> <span class="o">!=</span> <span class="no">nil</span> <span class="p">{</span>
        <span class="k">return</span> <span class="no">true</span>
    <span class="p">}</span>
    <span class="n">messageJSON</span><span class="p">,</span> <span class="n">err</span> <span class="o">:=</span> <span class="n">NewOfferMessageJSON</span><span class="p">(</span><span class="n">ps</span><span class="o">.</span><span class="n">client</span><span class="o">.</span><span class="n">userName</span><span class="p">,</span> <span class="n">offer</span><span class="p">)</span>
    <span class="k">if</span> <span class="n">err</span> <span class="o">!=</span> <span class="no">nil</span> <span class="p">{</span>
        <span class="k">return</span> <span class="no">true</span>
    <span class="p">}</span>

    <span class="k">if</span> <span class="n">err</span> <span class="o">=</span> <span class="n">ps</span><span class="o">.</span><span class="n">peerConnection</span><span class="o">.</span><span class="n">SetLocalDescription</span><span class="p">(</span><span class="n">offer</span><span class="p">);</span> <span class="n">err</span> <span class="o">!=</span> <span class="no">nil</span> <span class="p">{</span>
        <span class="k">return</span> <span class="no">true</span>
    <span class="p">}</span>
    <span class="n">flusher</span><span class="p">,</span> <span class="n">_</span> <span class="o">:=</span> <span class="n">ps</span><span class="o">.</span><span class="n">client</span><span class="o">.</span><span class="n">w</span><span class="o">.</span><span class="p">(</span><span class="n">http</span><span class="o">.</span><span class="n">Flusher</span><span class="p">)</span>

    <span class="n">fmt</span><span class="o">.</span><span class="n">Fprintf</span><span class="p">(</span><span class="n">ps</span><span class="o">.</span><span class="n">client</span><span class="o">.</span><span class="n">w</span><span class="p">,</span> <span class="s">"data: %s</span><span class="se">\n\n</span><span class="s">"</span><span class="p">,</span> <span class="n">messageJSON</span><span class="p">)</span>
    <span class="n">flusher</span><span class="o">.</span><span class="n">Flush</span><span class="p">()</span>
<span class="p">}</span>
<span class="k">return</span> <span class="no">false</span>



    

    




}

func dispatchKeyFrame(h *SSEHub) {

    for ps := range h.clients {

        for _, receiver := range ps.peerConnection.GetReceivers() {

            if receiver.Track() == nil {

                continue

            }

        <span class="n">_</span> <span class="o">=</span> <span class="n">ps</span><span class="o">.</span><span class="n">peerConnection</span><span class="o">.</span><span class="n">WriteRTCP</span><span class="p">([]</span><span class="n">rtcp</span><span class="o">.</span><span class="n">Packet</span><span class="p">{</span>
            <span class="o">&amp;</span><span class="n">rtcp</span><span class="o">.</span><span class="n">PictureLossIndication</span><span class="p">{</span>
                <span class="n">MediaSSRC</span><span class="o">:</span> <span class="kt">uint32</span><span class="p">(</span><span class="n">receiver</span><span class="o">.</span><span class="n">Track</span><span class="p">()</span><span class="o">.</span><span class="n">SSRC</span><span class="p">()),</span>
            <span class="p">},</span>
        <span class="p">})</span>
    <span class="p">}</span>
<span class="p">}</span>



    

    




}

Channels

I create channels in SSEClient and SSEHub.
I tried adding some channels into SSEClient to send messages from SSEHub first.

But if I did that, the application hang when I sent text messages after connecting WebRTC.
Because I think the cause is a circular reference, I remove these channels and send messages from SSEHub.

DEV Community

[Go] Try Pion/WebRTC with SSE

Intro

Environments

Connecting with WebRTC SFU

Samples

Client-side

main.page.ts

webrtc.controller.ts

Server-side

sseClient.go

peerConnectionState.go

sseHub.go

Channels

Resources

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