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?

1
68
11/19/2013 5:00:15 PM

Accepted Answer

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)
82
3/25/2012 2:42:10 AM

i would do something like this.

app.js

var app = require('http').createServer(handler),
    sockets = require('./sockets'),
    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);
  });
}

sockets.startSocketServer(app);
app.listen(80);

and sockets.js

var socketio = require('socket.io'),
        io, clients = {};

module.exports = {

        startSocketServer: function (app) {
                io = socketio.listen(app);

                // configure
                io.configure('development', function () {
                        //io.set('transports', ['websocket', 'xhr-polling']);
                        //io.enable('log');
                });

                io.configure('production', function () {
                        io.enable('browser client minification');  // send minified client
                        io.enable('browser client etag');          // apply etag caching logic based on version number
                        io.set('log level', 1);                    // reduce logging
                        io.set('transports', [                     // enable all transports (optional if you want flashsocket)
                            'websocket'
                          , 'flashsocket'
                          , 'htmlfile'
                          , 'xhr-polling'
                          , 'jsonp-polling'
                        ]);
                });
                //

                io.sockets.on('connection', function (socket) {
                        console.log("new connection: " + socket.id);

                        socket.on('disconnect', function () {
                                console.log("device disconnected");

                        });

                        socket.on('connect_device', function (data, fn) {
                                console.log("data from connected device: " + data);
                                for (var col in data) {
                                        console.log(col + " => " + data[col]);
                                }


                        });
                });
        }
};

i just copy&pasted some of my old code - don't really know what changed in the last versions of socket.io, but this is more about the structure than the actual code.

and i would only use 2 files for your purposes, not 3. when you think about splitting it up further, maybe one other file for different routes ...

hope this helps.


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