I'm trying to play Civilization V with my brother (who is on my network) and my friend (who is not on my network). I host a private internet game, enable 3 AI players, and invite them to the game. My brother can join without a problem, but when my friend joins it tells him that I disconnected (I still see him in the list but I do not receive his chat messages), even though I can still talk to my brother. It's like there are two different games going on, one with me and my brother, and one with my brother and his friend. If I try to start the game before my friend is disconnected (he is usually with us for a few seconds), Civ will freeze for a few moments, and then when it loads, it will just be my brother and me; my friend is kicked into his own game.
Why does this happen? We are not using Hamachi, and I have forwarded the port 4380 on both TCP and UDP. Is this the right port?
We are going to try using Hamachi, but we'd really rather not. (EDIT: We used Hamachi, it still didn't work.)