基于Licode demo的屏幕共享功能的实现

                                                                                                                           基于Licode demo的屏幕共享功能的实现
本文在licode的basicExample基础上添加screensharing功能。主要麻烦的是屏幕共享必须在https协议下传输，需要修改erizo controller的代码，而且https协议的证书问题也比较麻烦，目前的办法是手动添加证书到chrome中。chrome新版本需要使用插件screen capture,licode官方发布的插件不能直接在本地server上使用，需要修改后使用，下文将具体说。

1.index.html 修改，添加两个按钮，分别对应本地视频音频流和屏幕流

<button id="screenSharing" onclick="screenSharing()">Screen Sharing</button>
    <button id="localVideo" onclick="localVideo()">localVidoe</button>

　2.script.js 分别为screenSharing和localVidoe加载不同的localStream流。

function localVideo(){
  var config = {audio: true, video: true, data: true,  videoSize: [640, 480, 640, 480]};
  localStream = Erizo.Stream(config);
  initialize();
  console.info("localVidoe button has been clicked...");
}

function screenSharing(){
  var config = {screen: true, data: true, attributes: {name:'myStream'}};
  config.extensionId = "gieahgoflbnmfamkbfjafjkdgnkjmhch";
  localStream = Erizo.Stream(config);
  initialize();
  console.info("screenSharing button has been clicked...");
  
}

var serverUrl = "/";
var localStream, room, recording, recordingId;

function getParameterByName(name) {
  name = name.replace(/[[]/, "\[").replace(/[]]/, "\]");
  var regex = new RegExp("[\?&]" + name + "=([^&#]*)"),
      results = regex.exec(location.search);
  return results == null ? "" : decodeURIComponent(results[1].replace(/+/g, " "));
}

function testConnection () {
  window.location = "/connection_test.html";
}

function startRecording () {
  if (room !== undefined){
    if (!recording){
      room.startRecording(localStream, function(id) {
        recording = true;
        recordingId = id;
      });
      
    } else {
      room.stopRecording(recordingId);
      recording = false;
    }
  }
}


function localVideo(){
  var config = {audio: true, video: true, data: true,  videoSize: [640, 480, 640, 480]};
  localStream = Erizo.Stream(config);
  initialize();
  console.info("localVidoe button has been clicked...");
}

function screenSharing(){
  var config = {screen: true, data: true, attributes: {name:'myStream'}};
  config.extensionId = "gieahgoflbnmfamkbfjafjkdgnkjmhch";
  localStream = Erizo.Stream(config);
  initialize();
  console.info("screenSharing button has been clicked...");
  
}


window.onload=function(){
}
function initialize () {
  recording = false;
  var createToken = function(userName, role, callback) {

    var req = new XMLHttpRequest();
    var url = serverUrl + 'createToken/';
    var body = {username: userName, role: role};

    req.onreadystatechange = function () {
      if (req.readyState === 4) {
        callback(req.responseText);
      }
    };

    req.open('POST', url, true);
    req.setRequestHeader('Content-Type', 'application/json');
    req.send(JSON.stringify(body));
  };

  createToken("user", "presenter", function (response) {
    var token = response;
    console.log(token);
    room = Erizo.Room({token: token});

    localStream.addEventListener("access-accepted", function () {
      console.info('acess-accepted a client...');
      var subscribeToStreams = function (streams) {
        for (var index in streams) {
          var stream = streams[index];
          if (localStream.getID() !== stream.getID()) {
            room.subscribe(stream);
          }
        }
      };

      room.addEventListener("room-connected", function (roomEvent) {
    console.info('a client room connected...');
        room.publish(localStream, {maxVideoBW: 300});
        subscribeToStreams(roomEvent.streams);
      });

      room.addEventListener("stream-subscribed", function(streamEvent) {
        var stream = streamEvent.stream;
        var div = document.createElement('div');
        div.setAttribute("style", "  320px; height: 240px;");
        div.setAttribute("id", "test" + stream.getID());

        document.body.appendChild(div);
        stream.show("test" + stream.getID());

      });

      room.addEventListener("stream-added", function (streamEvent) {
        var streams = [];
        streams.push(streamEvent.stream);
        subscribeToStreams(streams);
        document.getElementById("recordButton").disabled = false;
      });

      room.addEventListener("stream-removed", function (streamEvent) {
        // Remove stream from DOM
        var stream = streamEvent.stream;
        if (stream.elementID !== undefined) {
          var element = document.getElementById(stream.elementID);
          document.body.removeChild(element);
        }
      });
      
      room.addEventListener("stream-failed", function (streamEvent){
          console.log("STREAM FAILED, DISCONNECTION");
          room.disconnect();

      });

      room.connect();

      localStream.show("myVideo");

    });
    localStream.init();
  });
};

3.修改licode_config.js ，将erizo controller改成https传输，因为屏幕共享必须在https协议下传输。host.key host.cert是openssl生成的。ip具体具体情况设置

config.erizoController.publicIP = '192.168.0.2'; //default value: ''
// Use '' to use the public IP address instead of a hostname
config.erizoController.hostname = ''; //default value: ''
config.erizoController.port = 8080; //default value: 8080
// Use true if clients communicate with erizoController over SSL
config.erizoController.ssl = true; //default value: false

config.erizoController.sslKey='/home/xxx/licode/myCert_chen/host.key';
config.erizoController.sslCert='/home/xxx/licode/myCert_chen/host.cert';

　　

4.修改erizoCtroller.js使其支持https

var fs=require('fs');

var http = require('http');
var https=require('https');
var config = require('./../../licode_config');

GLOBAL.config = config || {};

if(GLOBAL.config.erizoController.ssl){
    var options = {
        key: fs.readFileSync(GLOBAL.config.erizoController.sslKey).toString(),
        cert: fs.readFileSync(GLOBAL.config.erizoController.sslCert).toString()
    };
    var server = https.createServer(options);
}
else
    var server = http.createServer();

5.修改chrome插件licode/erizo_controller/erizoClient/extras/chrome-extension/manifest.json，并安装到chrome中。

"externally_connectable":

{

"matches":
["*://192.168.0.2/*"]

   },

6.修改extensinID,script.js和erizo.js中。externId可以在chrome插件设置dev模式查看。

7.打开https://192.168.0.2:3004链接，添加信任。然后打开https://192.168.0.2:8080/socket.io，添加到chrome信任列表中。特别是socket.io需要注意，如果不添加信任，则无法使用screen sharing功能，返回不安全的应答错误insecure response