socket.io: Failed to load resource
===

I'm trying to getting started with socket.io and node.js.

Following the first example on the socket.io's site I'm getting the following error in the browser's console:

    Failed to load resource: the server responded with a status of 404 (Not Found) http://localhost:3001/socket.io/socket.io.js
    Uncaught ReferenceError: io is not defined 

This is my server.js

    var app = require('express').createServer()
      , io = require('socket.io').listen(app);
    
    app.listen(3001);
    
    app.get('/', function (req, res) {
      res.sendfile(__dirname + '/index.html');
    });
    
    io.sockets.on('connection', function (socket) {
      socket.emit('news', { hello: 'world' });
      socket.on('my other event', function (data) {
        console.log(data);
      });
    });

And this is my index.html

    <!DOCTYPE html>
    <html>
      <head>
        <title></title>
        <meta charset="UTF-8" />
      </head>
      <body>
        <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>
      </body>
    </html>

I've already installed socket.io..