node.js + now.js setting up a server on the whole website

I successfully installed node and now and created a chat server with 3 rooms.

var fs = require('fs');
var server = require('http').createServer(function(req, response){
  fs.readFile('/var/www/www.domain.de/htdocs/multiroomchat.html', function(err, $
    response.writeHead(200, {'Content-Type':'text/html'});
    response.write(data);
    response.end();
  });
});
server.listen(8000);

I can now access this page via www.mydomain.com:8000. Right now I'm doing this for testing purposes only, but later I want to put that chat (ismiliar to the facebook chat) on my website. Therefor I have to have the chat server all over my page and not only on one file and without a port at the end of the domain. How is that possible? The chat server should be accessible on my whole website: www.mydomain.com/start/tutorial www.mydomain.com/imprint ... The chat will be displayed on every page.

Thanks!