set session id to socket in nodejs

socket.io.sessionID.js

/**
 * Module dependencies.
 */

var express = require('express');
var routes = require('./routes');
var user = require('./routes/user');
var http = require('http');
var path = require('path');

var app = express();

// all environments
app.set('port', process.env.PORT || 3000);
app.set('views', __dirname + '/views');
app.set('view engine', 'ejs');
app.use(express.favicon());
app.use(express.logger('dev'));
app.use(express.bodyParser());
app.use(express.cookieParser());
app.use(express.methodOverride());
app.use(express.cookieParser('your secret here'));
app.use(express.session({
  secret: 'secret',
  key: 'express.sid'
}));
app.use(app.router);
app.use(express.static(path.join(__dirname, '/../public')));
console.log(path.join(__dirname, '../public'));


// development only
if ('development' == app.get('env')) {
  app.use(express.errorHandler());
}


app.get('/', routes.index);
app.get('/teacher', routes.teacher);
app.get('/blackbord', routes.blackbord);
app.get('/users', user.list);


var server = http.createServer(app);
server.listen(app.get('port'), function() {
  console.log('Express server listening on port ' + app.get('port'));
});


function test() {
  console.log('test pass a func');
}

////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////

var teacherSocket;
var studentSocket;
var roomId = "123456";

//----socketIo 
var io = require('socket.io').listen(server);

//----set sessionID
var cookie = require("cookie");
io.set('authorization', function (data, accept) {
    // check if there's a cookie header
    if (data.headers.cookie) {
        // session id, as you specified in the Express setup.
        data.sessionID = cookie.parse(data.headers["cookie"])["express.sid"];
    } else {
       // if there isn't, turn down the connection with a message
       // and leave the function.
       return accept('No cookie transmitted.', false);
    }
    // accept the incoming connection
    accept(null, true);
});
io.sockets.on('connection', function(socket) {
  console.log('sesssionID', socket.handshake.sessionID);
  socket.join(socket.handshake.sessionID);
  //--- 通过 辨别身份
});