multi-player gamecenter programming - best way to get started?

I plan to write a small demo app that allows several players to exchange text messages (and probably voice messages) while playing a multi-player game on the iphone. Also other type of data will have to be shared among the participants of the players.

GameCenter seems to be the right way to go. But I don't find a suitable sample code anywhere. I checked GKTank but it just works over bluetooth connecting 2 players. In my g开发者_StackOverflow中文版ame more than 2 players will be part of the game - connected through the GameCenter - not p2p bluetooth.

What is the best place to get started? Is there a SAMPLE CODE showing all the main GameCenter code pieces required to write a basic multi-player game?

Thank you very much!

This seems to be a good starting point. A nice little introduction with server side and client. http://www.crocodella.com.br/2010/12/creating-a-multiplayer-abstraction-layer-with-gamecenter-and-asyncsocket/