What Port Does Android Use For VPN Connections?

I'm trying to set up a VPN so that I can have a connection to my LAN from my phone (HTC Droid Incredible, Stock ROM, Not rooted) wherever I am. AFAICT, everything is set up correctly. The Domain Name resolves correctly, I forwarded the ports required by the how-to I was following, yet I still can't connect. I have no idea what's wrong or how to get to any debug information. The only thing I can think of that I haven't verified yet is the port, but I couldn't find a way to select one. What Port Does Android Use For VPN Connections? P.S. I would *really* like to do this without rooting.