If you are wanting to create an online game using blender, you may of heard that to have a fast server, you should create it in C++.
Well many people also work with the networking library called SDL_net but it is very hard to get start with it. I have created a tutorial which will get you started and creating your own server using C++ and SDL_net from scratch.
Knowledge of C++ would be very good since this isn't easy stuff but I did start it off assuming you are new to this.
I also created a simple python client for the reason that you can implement it into blender to create your own game and using a powerful C++ server.
check out and tell me what you think of the tutorial