Can't load socket.io.js

I'm creating an app that has separate server and client code (two different git repositories).

The HTML is there just as a UI, but it still needs to load /socket/socket.io.js in order to communicate with the server.

This is my HTML:

<html>
    <head>
        <script src="/socket/socket.io.js"></script>
        <script src="js/myStuff.js"></script>
    </head>

    <body>
    </body>
</html>

When queried with an address that starts with /c, the server will automatically replace the prefix with the client code directory. So, the website is loaded like this: localhost:8080/c/index.html, and the request for js/myStuff.js is actually /c/js/myStuff.js.

This is how it's all implemented:

var http = require("http");
var io = require("socket.io");
var fs = require("fs");
var iniparser = require("iniparser");

var config = iniparser.parseSync('./config.ini');

clientPath = config.server.clientPath; //   ../../Bla

var handler = function(req, res)
{    
    if (req.url[1] == "c")
    {
        req.url = req.url.slice(2, req.url.length); //Cut off the "/c"
        url = __dirname + "/" + clientPath + req.url;
    }
    else
    {
        url = req.url; //Nothing.
    }

    fs.readFile (url, function(err, data)
    {
        if (err)
        {
            res.writeHead(404);
            return res.end("File not found.");
        }

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

var server = http.createServer(handler);
server.listen(8080);
var socket = io.listen(server);

Both myStuff.js and index.html load correctly, but there is a problem with loading /socket/socket.io.js. That is very, very strange, because I don't even touch the address.

This error is given by Google Chrome:

GET http://localhost:8080/socket/socket.io.js 404 (Not Found)

Why is this happening and how can I fix it?

It doesn't look as if you are changing it anywhere so the default location for the Socket.io JavaScript is

<script src="/socket.io/socket.io.js"></script>

not socket/socket.io.js.