What is in door 21, 80, and 443 on my computer?
Chris Pietschmann created a simple port scanner using VB.Net. The interesting thing with the scanner is it uses ThreadPool class to help queue up work units! This means is the work is executed asynchronously and in an orderly fashion. Over all, great example of network scanning and threading.
Best of all, Chris even has the example in multiple versions of Visual Basic!