server.js

//express3.0
var express = require('express');
var app = express();
app.set('port', 3000);
app.set('views', __dirname + '/views');
app.set('view engine', 'jade');
app.use(express.bodyParser());
app.use(express.methodOverride());

//session & cookie
var sessionStore = new express.session.MemoryStore({reapInterval: 60000 * 10});
app.use(express.cookieParser());
app.use(express.session({
  store: sessionStore,
  key: 'sid',
  secret: 'your_session_secret'
}));

app.use(express.static(path.join(__dirname, 'public')));
app.use(app.router);
var server = http.createServer(app);
var io = require('socket.io').listen(server);
server.listen(app.get('port'), function(){
  console.log("%s listening on port %d in %s mode", 'your_project_name', app.get('port'), app.settings.env);
  console.log("God bless love....");
  console.log("You can visit your app with http://localhost:%d", app.get('port'));  
});

//通过cookie读取sessionid,进而得到session
var chatServer = io.of('/chat');
chatServer.authorization(function(handshakeData, callback) {
  //没有cookie则退出
  if (!handshakeData.headers.cookie) return callback('socket.io: no found cookie.', false);

  //根据cookie找sessionId,https://github.com/DanielBaulig/sioe-demo/blob/master/app.js
  var signedCookies = require('express/node_modules/cookie').parse(handshakeData.headers.cookie);
  handshakeData.cookies = require('express/node_modules/connect/lib/utils').parseSignedCookies(signedCookies, 'your_session_secret');

  //根据sessionId找username
  sessionStore.get(handshakeData.cookies['sid'], function(err, session) {
    if (err || !session) return callback('socket.io: no found session.', false);
    //得到session存入handshakeData
    handshakeData.session = session;
    if (handshakeData.session.user) {
      return callback(null, true);
    } else {
      return callback('socket.io: no found session.user', false);
    }
  })
});

chatServer.on('connection', function (client) {
  //读取session
  var username = client.handshake.session.user.username;
});