OneCard now has the ability to allow multiplayer games over local (rendezvous) networks.  However, due to the fact that I don't have a large network on which to test OneCard, the multiplayer aspects of the game have not been fully beta-tested.  

I have tested multiplayer games with 2 or 3 computers on a network connected to an Ethernet router.  I have not been able to test whether OneCard will allow two separate multiplayer games to take place on the same network at the same time.  This should work, but I haven't been able to test it as I don't have 4 computers.

I strongly encourage you to read the online help re multiplayer games.

I have not been able to program OneCard to successfully change the host of a multiplayer game without disconnecting all the clients first.  Therefore if the host leaves the list of available players in the multiplayer window, all the other players will be removed as well.  This will happen even if the host only leaves because they have started a game.  The host has to leave the list of available players when they start a game to prevent new players from trying to connect to the host in the middle of a game.  This may seem inconvenient for the players left behind, but I haven't managed to find a way around it.

I would appreciate any feedback on the multiplayer aspect of OneCard.  If you experience crashes, unexpected "host has left the game" messages or are unable to start a multiplayer game, please email me at ewhan@mac.com with details of the problem.  

If you are unable to see any players in the available players list in the multiplayer window, check that you have ports 1234 and 1235 open for TCP.  Try turning off the firewall in the System Preferences Sharing preference pane and any other firewall software you might have installed.

If you see a message such as "Couldn't initialise send port" when you are trying to host a game, try joining the game again.  If that still doesn't work, ask another player to host the game or quit and restart OneCard.