Making (threaded) game server in C++/WinSock

Question

I have a game I am working on in C++ and OpenGL. I have made a threaded server that right now accepts clients (the game) and receives messages from them. Right now the game only sends messages. I want both the game and server to be able to send and receive, but I'm not sure the best way to go about it. I was considering using a thread for sending and one for receiving, both on the same socket. Right now the game runs in a single thread, and the server makes a separate thread for each client.

Looking for suggestions on how to go about it for the game as well as the server (unless your suggestion is the same for both). Any questions, feel free to ask :)

Thanks!

Answer 1

Consider using Boost.ASIO that implements this well with a C++ API (allowing many different approaches besides just asynchronous I/O). There are plenty of tutorials. However, for the absolute highest performance, you should probably not use threads.

Answer 2

What you need to do is set up an outgoing queue of messages for each client. Say you have 2 clients connected to the server, one being serviced by thread A and the other by thread B. Thread A should do a WaitOnMultipleObjects() on its socket and on a semaphore/mutex/condition variable for its queue. That way, if it gets something in its queue, it can wake up and send it out. If it gets a message from the client that it needs no give to client B, it will process that message and put it in thread B's outgoing queue.

This is a very simple synchronization scheme. If your game is very complex or massive, you will have to do something much more clever than this.

Answer 3

Don't use threads in a game server. Many professional, AAA game servers are single-threaded - every one I've ever seen, in fact.