流媒体学习之路(mediasoup)——信令传输（3）

流媒体学习之路(mediasoup)——信令传输（3）

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一、Node.js部分

  mediasoup——c++部分的信令交互主要通过Socket管道来进行的。Node.js部分与c++部分通过本机网络进行通话，实现交互。
前面两篇提到，Node.js部分worker建立后需要建立channel来进行通信，我们再来回顾一下channel.js部分通信的代码。下面是Worker的构造函数：

 constructor({
    
     logLevel, logTags, rtcMinPort, rtcMaxPort, dtlsCertificateFile, dtlsPrivateKeyFile, appData }) {
   
   
        super();
        // Closed flag.
        this._closed = false;
        // Routers set.
        this._routers = new Set();
        // Observer instance.
        this._observer = new EnhancedEventEmitter_1.EnhancedEventEmitter();
        logger.debug('constructor()');
        let spawnBin = workerBin;
        let spawnArgs = [];
        if (process.env.MEDIASOUP_USE_VALGRIND === 'true') {
   
   
            spawnBin = process.env.MEDIASOUP_VALGRIND_BIN || 'valgrind';
            if (process.env.MEDIASOUP_VALGRIND_OPTIONS)
                spawnArgs = spawnArgs.concat(process.env.MEDIASOUP_VALGRIND_OPTIONS.split(/\s+/));
            spawnArgs.push(workerBin);
        }
        if (typeof logLevel === 'string' && logLevel)
            spawnArgs.push(`--logLevel=${
     
     logLevel}`);
        for (const logTag of (Array.isArray(logTags) ? logTags : [])) {
   
   
            if (typeof logTag === 'string' && logTag)
                spawnArgs.push(`--logTag=${
     
     logTag}`);
        }
        if (typeof rtcMinPort === 'number' && !Number.isNaN(rtcMinPort))
            spawnArgs.push(`--rtcMinPort=${
     
     rtcMinPort}`);
        if (typeof rtcMaxPort === 'number' && !Number.isNaN(rtcMaxPort))
            spawnArgs.push(`--rtcMaxPort=${
     
     rtcMaxPort}`);
        if (typeof dtlsCertificateFile === 'string' && dtlsCertificateFile)
            spawnArgs.push(`--dtlsCertificateFile=${
     
     dtlsCertificateFile}`);
        if (typeof dtlsPrivateKeyFile === 'string' && dtlsPrivateKeyFile)
            spawnArgs.push(`--dtlsPrivateKeyFile=${
     
     dtlsPrivateKeyFile}`);
        logger.debug('spawning worker process: %s %s', spawnBin, spawnArgs.join(' '));
        this._child = child_process_1.spawn(
        // command
        spawnBin, 
        // args
        spawnArgs, 
        // options
        {
   
   
            env: {
   
   
                MEDIASOUP_VERSION: '3.6.13'
            },
            detached: false,
            // fd 0 (stdin)   : Just ignore it.
            // fd 1 (stdout)  : Pipe it for 3rd libraries that log their own stuff.
            // fd 2 (stderr)  : Same as stdout.
            // fd 3 (channel) : Producer Channel fd.
            // fd 4 (channel) : Consumer Channel fd.
            // fd 5 (channel) : Producer PayloadChannel fd.
            // fd 6 (channel) : Consumer PayloadChannel fd.
            stdio: ['ignore', 'pipe', 'pipe', 'pipe', 'pipe', 'pipe', 'pipe'],
            windowsHide: true
        });
        this._pid = this._child.pid;
        this._channel = new Channel_1.Channel({
   
   
            producerSocket: this._child.stdio[3],
            consumerSocket: this._child.stdio[4],
            pid: this._pid
        });
        this._payloadChannel = new PayloadChannel_1.PayloadChannel({
   
   
            // NOTE: TypeScript does not like more than 5 fds.
            // @ts-ignore
            producerSocket: this._child.stdio[5],
            // @ts-ignore
            consumerSocket: this._child.stdio[6]
        });
        this._appData = appData;
        let spawnDone = false;
        // Listen for 'running' notification.
        this._channel.once(String(this._pid), (event) => {
   
   
            if (!spawnDone && event === 'running') {
   
   
                spawnDone = true;
                logger.debug('worker process running [pid:%s]', this._pid);
                this.emit('@success');
            }
        });
        this._child.on('exit', (code, signal) => {
   
   
            this._child = undefined;
            this.close();
            if (!spawnDone) {
   
   
                spawnDone = true;
                if (code === 42) {
   
   
                    logger.error('worker process failed due to wrong settings [pid:%s]', this._pid);
                    this.emit('@failure', new TypeError('wrong settings'));
                }
                else {
   
   
                    logger.error('worker process failed unexpectedly [pid:%s, code:%s, signal:%s]', this._pid, code, signal);
                    this.emit('@failure', new Error(`[pid:${
     
     this._pid}, code:${
     
     code}, signal:${
     
     signal