Well, I have a cable that connects me to the internet, and in System Preferences, it's called 'Built in Ethernet'. I don't see any way to alter the router or ports.
I don't think the problem is there, though. I can load a map and all that easily, but my brother can't find me in the listings. He's not in the same house as me, anyway. Also, when I'm in a loaded map, in 'About', it says that it's local. Should I be setting the 'Dedicated Server' option to LAN, maybe?