when you say GAME SERVER what do you mean? like how to launch a gameserver on the net using an existing computer? or actually building a physical PC to use as a PC game dedicated server? and for the consoles just read the booklet for the game you wanna host a game for. it should tell you how to do it.
If you mean just playing games over a lan, all you need as either a couple of ethernet cards and a straight through ethernet cable, or a Router otherwise pm me for more detials on how to build a "game hosting server"