I could be totally speaking out of my ass here, because I honestly did very little digging at the network level of Warcraft 3 apart from things relating to unit commands, but it was my understanding that in a custom game it is up to the host client to maintain the connections of all of the players and not the game server (which is the case in ladder games).
Meaning the host would be the only one with access to every IP address in the game. I'm not certain on this, though.
Meaning the host would be the only one with access to every IP address in the game. I'm not certain on this, though.