The Torque Network Library is a robust, secure, easy to use, cross-platform 
C++ networking API designed for high performance simulations and games. The 
network architecture in TNL has powered some of the best internet 
multiplayer action games to date. Whether you're writing a multiplayer game, 
developing a complex simulation, or just need a solid foundation for network 
apps, TNL will meet your needs.

TNL is available under the GNU General Public License (GPL), an indie 
license, and a commercial license.

WWW: http://opentnl.org