Grapple is designed to be a simple network layer, allowing the addition of multiplayer features to a game for as little as a dozen lines of code.

however it is also fully featured, so if you want more from your networking, you can have it.

basic features
* simple client-server networking
* keeps all clients aware of all other clients
* passworded servers
* data transfer via tcp, udp, or reliable udp
advanced features
* network messenging by either a push or a pull model, or a mixture of both
* multiple methods of querying users
* user groups for client bandwidth saving
* network load reacting data transmission and retransmission
* background pinging to monitor network states
* server failover
* a fully functional lobby system
homepage: http://grapple.linuxgamepublishing.com/