ok here goes, even though tcp/ip and lan protocol is supported in gp4 it does not run as well as ea's f1_2001/2 and papyrus grand prix legends. Use gpx_patch 3.03, both machines must have identical, repeat identical games, both machines should be on cable or at the minimum broadband adsl or on the same isp in preferably the same street, also once a succesful connection has been made a dramatic drop in framerate usually occurs rendering the game impossible to play, try 2 minutes to turn one at Albert Park. If you really want to race your bro online get gpl or f1_2002. They are worth having anyway, you just have to have them all
ps. they are sims, not games, gpx_patch is on this site and we all play together here
have fun