Separating file server and socket.io logic in node.js

Question

I'm fairly new to node.js and I've found its quite complicated separating a project into multiple files as the project grows in size. I had one large file before which served as both a file server and a Socket.IO server for a multiplayer HTML5 game. I ideally want to separate the file server, socket.IO logic (reading information from the network and writing it to a buffer with a timestamp, then emitting it to all other players), and game logic.

Using the first example from socket.io to demonstrate my problem, there are two files normally. app.js is the server and index.html is sent to the client.

app.js:

var app = require('http').createServer(handler)
  , io = require('socket.io').listen(app)
  , fs = require('fs')

app.listen(80);

function handler (req, res) {
  fs.readFile(__dirname + '/index.html',
  function (err, data) {
    if (err) {
      res.writeHead(500);
      return res.end('Error loading index.html');
    }

    res.writeHead(200);
    res.end(data);
  });
}

io.sockets.on('connection', function (socket) {
  socket.emit('news', { hello: 'world' });
  socket.on('my other event', function (data) {
    console.log(data);
  });
});

index.html:

<script src="/socket.io/socket.io.js"></script>
<script>
  var socket = io.connect('http://localhost');
  socket.on('news', function (data) {
    console.log(data);
    socket.emit('my other event', { my: 'data' });
  });
</script>

To separate file server and game server logic I would need the function "handler" defined in one file, I would need the anonymous function used a callback for io.sockets.on() to be in another file, and I would need yet a third file to successfully include both of these files. For now I have tried the following:

start.js:

var fileserver = require('./fileserver.js').start()
  , gameserver = require('./gameserver.js').start(fileserver);

fileserver.js:

var app = require('http').createServer(handler),
    fs = require('fs');

function handler (req, res) {
  fs.readFile(__dirname + '/index.html',
  function (err, data) {
    if (err) {
      res.writeHead(500);
      return res.end('Error loading index.html');
    }

    res.writeHead(200);
    res.end(data);
  });
}

module.exports = {
    start: function() {
        app.listen(80);
        return app;
    }
}

gameserver:

var io = require('socket.io');

function handler(socket) {
    socket.emit('news', { hello: 'world' });
    socket.on('my other event', function (data) {
        console.log(data);
    });
}

module.exports = {

    start: function(fileserver) {       
        io.listen(fileserver).on('connection', handler);
    }

}

This seems to work (the static content is properly served and the console clearly shows a handshake with Socket.IO when the client connects) although no data is ever sent. It's as though socket.emit() and socket.on() are never actually called. I even modified handler() in gameserver.js to add console.log('User connected'); however this is never displayed.

How can I have Socket.IO in one file, a file server in another, and still expect both to operate correctly?

do you know the express js framework? expressjs.com it's great and really helps you structure your application. there are a ton of examples on github (github.com/visionmedia/express/tree/master/examples) maybe there's something that can help you with your problem... — Philipp Kyeck
@pkyeck: I'm reading up on expressjs now to try and figure out how it can benefit me, but so far it seems more complicated than what I need. All I really want is to separate my logic for the game server and the file server into two separate files then have a third file which properly starts both servers. — stevendesu
@pkyeck I've looked at it, although it seems like it's only masking the problem and not solving it. Not sockets.js is the ONE MASSIVE FILE instead of app.js. I'd like to have no single massive files but instead separate files for every function. More and more node.js seems like more of a hassle than a blessing. — stevendesu

Ricardo Tomasi Ricardo Tomasi · Accepted Answer · 2012-03-25T02:42:10

In socket.io 0.8, you should attach events using io.sockets.on('...'), unless you're using namespaces, you seem to be missing the sockets part:

io.listen(fileserver).sockets.on('connection', handler)

It's probably better to avoid chaining it that way (you might want to use the io object later). The way I'm doing this right now:

// sockets.js
var socketio = require('socket.io')

module.exports.listen = function(app){
    io = socketio.listen(app)

    users = io.of('/users')
    users.on('connection', function(socket){
        socket.on ...
    })

    return io
}

Then after creating the server app:

// main.js
var io = require('./lib/sockets').listen(app)

Separating file server and socket.io logic in node.js

4 Answers