Getting the current user in express.js, while using socket.io?

Question

I'm using the express framework, and part of my web app uses socket.io to enable real-time chat. I need to get the current user's username, and create a room with him in it. The problem is I can't find a way to get the user info when socket.on('connection') is called. Here's the relevant code I have so far :

var express = require('express');
var passport = require('passport');                                                                                    
var LocalStrategy = require('passport-local').Strategy;                                                                
var mongoose = require('mongoose');                                                                                    
var session = require('express-session');                                                                              
var http = require('http');
var routes = require('./routes/index');
var app = express();                                                                                                   
var server = http.createServer(app);                                                                                   
var io = require('socket.io')(server);                                                                                 

server.listen(4000);
app.use(session({secret : 'anything',                                                                                  
    saveUninitialized: true,                                                                                           
    resave: true}));                                                                                                   
app.use(passport.initialize());                                                                                        
app.use(passport.session());

mongoose.connect('mongodb://localhost/my_db');
var Schema = mongoose.Schema;                                                                                          
var UserDetail = new Schema({                                                                                          
    username: String,                                                                                                  
    password: String                                                                                                   
}, {                                                                                                                   
    collection: 'users'                                                                                                
});                                                                                                                    
var UserDetails = mongoose.model('users', UserDetail);                                                                 

app.use('/', routes);                                                                                                  
app.use('/users', users);                                                                                              

app.post('/login',                                                                                                     
        passport.authenticate('local', {                                                                               
            successRedirect: '/loginSuccess',                                                                          
            failureRedirect: '/loginFailure',                                                                          
        })                                                                                                             
        );

io.on('connection', function(socket) {                                                                                 
    console.log('socket stuff');                                                                                       
    var sessionStore = session;                                                                                        
    var sessionId    = socket.handshake.sessionId;                                                                     

    sessionStore.get(sessionId, function(err, session) {                                                               
        if(!err) {                                                                                                     
            console.log('no error');                                                                                   
            if(session.passport.user) {                                                                                
                console.log('This is the users email address %s', session.passport.user);                              
            }                                                                                                          
        }                                                                                                              
    });                                                                                                                
    socket.emit('newMessage', {content : 'Chat message content'});                                                     
});

The last function is where I'm having trouble. When a user requests a page, I can just find their username by req.user, but I have no idea how to do it when I don't have req. The code I have for sessions in io.on('connection') does not work at all, and just throws errors, figured I'd keep it in to show what I've tried so far.

Answer 1

This has been asked a few times but the older answers I found do not work anymore. The answer lies in parsing socket.handshake.headers.cookie but this is hacky and will depend on the internals of express-session.

Anyways, this should work for now with Express 4 and socket.io 1.1:

var express   = require('express'),
    session   = require('express-session'),
    cookie    = require('cookie'),
    signature = require('cookie-signature');

var app    = express(), 
    store  = new session.MemoryStore(),
    secret = 'session-secret-key',
    name   = 'connect.sid';

app.use(session({
  name:   name,
  secret: secret,
  store:  store,
  resave: true,
  saveUninitialized: true
}));

var server = require('http').createServer(app),
    io     = require('socket.io')(server);

io.on('connection', function(socket) {
  if (socket.handshake && socket.handshake.headers && socket.handshake.headers.cookie) {
    var raw = cookie.parse(socket.handshake.headers.cookie)[name];
    if (raw) {
      // The cookie set by express-session begins with s: which indicates it
      // is a signed cookie. Remove the two characters before unsigning.
      socket.sessionId = signature.unsign(raw.slice(2), secret) || undefined;
    }
  }
  if (socket.sessionId) {
    store.get(socket.sessionId, function(err, session) {
      console.log(session);
    });
  }
});