how can I get sessions to work using redis, express & socket.io?

inside the io.configure, you have to link the socket with the http session.

Here's a piece of code that extracts the cookie (This is using socket.io with xhr-polling, I don't know if this would work for websocket, although I suspect it would work).

var cookie = require('cookie');var connect = require('connect');var sessionStore = new RedisStore({  client: redis // the redis client});socketio.set('authorization', function(data, cb) {  if (data.headers.cookie) {    var sessionCookie = cookie.parse(data.headers.cookie);    var sessionID = connect.utils.parseSignedCookie(sessionCookie['connect.sid'], secret);    sessionStore.get(sessionID, function(err, session) {      if (err || !session) {        cb('Error', false);      } else {        data.session = session;        data.sessionID = sessionID;        cb(null, true);      }    });  } else {    cb('No cookie', false);  }});

Then you can access the session using:

socket.on("selector", function(data, reply) {  var session = this.handshake.session;  ...}

This also has the added benefit that it checks there is a valid session, so only your logged in users can use sockets. You can use a different logic, though.

Looking at your last note (won't be able to share its state over multiple processes using redis) I had the same problem and found a solution:

var express = require("express.io");var swig = require('swig');var redis = require('redis');var RedisStore = require('connect-redis')(express);workers = function() {    var app = express().http().io();    app.use(express.cookieParser());    app.use(express.session({        secret: 'very cool secretcode',        store: new RedisStore({ client: redis.createClient() })    }));    app.io.set('store', new express.io.RedisStore({        redisPub: redis.createClient(),        redisSub: redis.createClient(),        redisClient: redis.createClient()    }));    app.get('/', function(req, res) {        res.render('index');    });    app.listen(3000);    app.io.route('ready', function(req){        //setup session stuff, use session stuff, etc.  Or make new routes    });};cluster = require('cluster');numCPUs = require('os').cpus().length;if (cluster.isMaster){    for (var i = 0; i < numCPUs; i++)    {        cluster.fork();    }}else{    workers();}