Hello, I was wondering is there an easy way to communicate between iphones over the Internet(Not LAN/Bluetooth) or must there be a dedicated server in which all the iphones running an application needs to connect to?

For instance, suppose I'm writing a game which works on the Internet. Once four clients joins a room, game starts. must I implement a server in which every Iphone client connects to (for instance if server was developed on Windows it could be a Service) or is there another way to address this when developing Internet-based application?

Thank you