I was out of town this week and I was thinking it would be nice to have the ability to very easily open outside ports for people who don't know that NAT is not some kind of bug. Mostly I just wanted to play with Universal Plug-n-Play (UPnp), since I knew nothing about it.
I found a UPnp library for Java called, surprise, upnplib, and integrated it into a Servlet Context Listener. It takes 2 options in the web.xml file, upnp.enabled and upnp.port. The port should be auto discovered, but currently is not. One thing at a time. In the mean time, set it to 8080 or 8084 if you're using NetBeans, and the port will be open to the public when the application starts and closed when it exits.