This week's giveaway is in the EJB and other Java EE Technologies forum. We're giving away four copies of EJB 3 in Action and have Debu Panda, Reza Rahman, Ryan Cuprak, and Michael Remijan on-line! See this thread for details.
Run netstat command on the command line. It will tell you which application is listening on which ports. I think the parameters to netstat change based on OS, although I might be wrong there. Look at the help for netstat