For clarity the router I used was my own Linux based one, so it wasn't off the shelf. I'd have happily port forwarded it, but the android version didn't need it so why the Linux one?
I've not used Skype so I can't say, but anyone who's used an XBox console online knows about the port forwarding nightmares you have to go through to make the things work correctly. UPnP was the only way to make 2 consoles work at the same time.
