Let's say that I have a several clients connected to a server, and therefore have several references to client connection sockets stored in the server. When an FB_READ message is received, how do I know which connection socket I should call recv() on? ...stip

The variable "wParam" that is passed whenever you get a WSAASYNC notice is your socket, so you could call, say,

recv(wParam, (char*)&data, sizeof(data));

And it will always be the socket you got data from. Pretty nifty.