Clonk Rage (www.clonk.de) is not 3d, but it's a quite complex 2d game which runs under windows, linux and mac
the masterserver is located @ http://www.clonk.de:84/league/server
and is written in some kind of an ini format
launching a game when the ip is known is done with
"./clonk clonk://$ip$/"
or
"./clonk /join:$ip$"
i don't know if it makes sense implementing clonk rage support, since the "servers" are player hosted games
but it would be a real awesome treat