Postina: A Publish/Subscribe Middleware Designed for Massively Multiplayer Games

In MMOGs, numerous messages such as state updates are sent to different clients. While some messages must be multicast to a large group of clients, other messages are private and sent to a single client only. Using a traditional client-server approach limits the number of simultaneous players, a property that is undesired in MMOGs. A potential solution would be to use publish/subscribe systems which are designed for scalability. Pure publish/subscribe systems, however, do not provide any possibility to send a message directly to a single client as the peers do not have any knowledge of the network topology.