app.js

var express = require("express"),
    http = require("http"),
    async = require("async"),
    sockjs = require("sockjs"),
    uuid = require("uuid"),
    url = require("url"),
    redis = require("redis"); // for pubsub and to persist data if your app restarts
    
var app = express(),
    redisClient = redis.createClient(),
    pubsubClient = redis.createClient();
 
app.use(app.router);
 
var settings = {
  port: 80
  prefix: "/sockets"
};
 
 
app.get("/", function(req, res){
  var id = uuid.v4();
  redisClient.set(id, 0, function(error){
    if(error){
      console.log("Error creating room in redis!", error);
      res.render(500, "500.html"); // send them a page with an internal server error message
    }else{
      res.redirect("/" + id);
    }
  });
});
 
app.get("/:id", function(req, res){
  res.render("chat.html"); // send them a page with sockjs and the chat interface
});
 
 
var server = http.createServer(app),
    socketServer = sockjs.createServer();
 
socketServer.installHandlers(server, { 
		prefix: settings.prefix, // can be anything, just make sure the client also implements this 
});
 
/*
  When a socket attempts to connect from the client side have the socket append the path suffix to the connection url as a GET parameter
  For example, if the client is at the url http://yourapp.com/12345 then in the browser the sockjs initialization would look like:
    var sock = new SockJS('http://yourapp.com/your_prefix_to_match_settings.prefix?room=12345')
*/
 
var sockets = {};
 
pubsubClient.on("message", function(channel, message){
  if(typeof message === "object")
    message = JSON.stringify(message);
  if(sockets[channel]){
    async.each(Object.keys(sockets[channel]), function(sid, callback){
      sockets[channel][sid].write(message);
      callback();
    }, function(error){
      // there shouldn't be any errors here...
    });
  }
});
 
 
sockets.on("connection", function(socket){
  var room = url.parse(socket.url, true).query.room;
  if(room){
    redisClient.incr(room, function(error, members){
      if(error){
        console.log("Error incrementing room member count!", error);
        // TODO maybe close the client too?
      }else{
        socket.sid = uuid.v4();
        if(members === 1){
          pubsubClient.subscribe(room);
          sockets[room] = {};
        }
        sockets[room][socket.sid] = socket;
      }
    });
  }else{
    // no room found, kill the connection
    return socket.end(); 
  }
  
  socket.on("data", function(message){
    // assume the messages are stringified json from the client
    pubsubClient.publish(room, message);
  });
  
  socket.on("close", function(){
    delete sockets[room][socket.sid];
    redisClient.incrby(room, -1, function(error, members){
      if(error)
        console.log("Error decrementing room member counter!", error);
      else if(members === 0)
        delete sockets[room];
    });
  });
});
 
 
server.listen(settings.port, function(){
  console.log("Server started");
});