neegah if you're on the same network as the guy who wants to join you then you don't have to port forward at all and upnp also doesn't matter. your game says it uses port 4977? That shouldn't be the case if it's the only instance of the game running on your pc..
Anyways if he's on the same network it should just work via
You could try disabling your windows firewall if it doesn't work.