I've been following this(<http://socket.io/get-started/chat/>) tutorial on how to make a simple chat application using socket.io.

I tried to however use Express to create it and I was wondering why port 3000 is already in use? The code below will not work unless I change the port number.

```
/* Make the http server listen on port 3000. */
http.listen(3000, function(){
 console.log('listening on *:3000');
});

```

Does express use the port to do other things like routing or something?
Is there a simple way to find what is happening on that port?

I may also be doing something dodgy with my require things:

```
var express = require('express');
var app = require('express')();
var http = require('http').Server(app);
var router = express.Router();
var io = require('socket.io')(http);

```

Thanks.