the kbengine is awesome. scalable, free and works for ogre and unity 3d. unreal engine 4 ports expected
A mmog engine of server(kbengine), open sources
What is KBEngine?
An open source MMOG server engine, Using a simple protocol will be able to make the client and server interaction, To use the KBEngine-plugins quick combine with (Unity3D, OGRE, Cocos2d, HTML5, etc.) to form a complete client.
Engine framework written using c++, Game logic layer using Python(Support the hotfix), developers do not need to re-implement some common server-side technology, Allows developers to concentrate on the game logic development, quickly create a variety of games.
(Frequently asked load-limit, kbengine is designed to be multi-process distributed dynamic load balancing scheme, In theory only need to expand hardware can increase load-limit, The single machine load-limit depends on complexity of logic of the game itself.)
unity3d : https://github.com/kbengine/kbengine_unity3d_demo
unity3d : https://github.com/kbengine/kbengine_unity3d_warring
ogre : https://github.com/kbengine/kbengine_ogre_demo
html5 : https://github.com/kbengine/kbengine_html5_demo
API : https://github.com/kbengine/kbengine…master/kbe/doc
tutorial : https://github.com/kbengine/kbengine…aster/tutorial
online_docs : http://www.kbengine.org/docs/