**Summary**: How can I use Node.js to see whether something is listening on a given port?

**Details**: 

I am writing tests for an HTTP-based application in Node. 

I've extended Node's `http.Server` with `util.inherits`, and in the resulting "class" wrap the standard `.listen()` functionality in a method of my own called `.start()`. This method performs some setup (e.g. connects to MongoDB) and then calls `http.Server.listen(port, cb)` when everything is good to go. 

My problem: I'd like to write a test that calls `.start()` and then checks that the server is, indeed, listening on the specified port. I would like to do this without sending an HTTP request for the server to field. I just want to test that the server is listening. 

Unfortunately, I am not familiar with TCP, but given my experience with port scanning and `netstat` and things of that nature, I have the impression that *something* in Node's [net](http://nodejs.org/api/net.html) package will let me do this. Is this possible?