Hamachi is a centrally-managed zero-configuration virtual private network (VPN) freeware application capable of establishing direct links between computers that are behind NAT firewalls without requiring reconfiguration.
To play a game, you can either create a network and give its name and password to a freind to join. Or you can google for a network playing your favourite game. try googling “hamachi yourgamesname“.
On hamachi you can play any game that supports network play even if it do not support internet play.