A client is any program that can connect to a server.
There are a three major types of client-server connnections. Here is a list with clients on the left and servers on the right:
- game client/bot --> game server (Game Protocol)
- game server --> billing server (Billing Protocol)
- directory client/game client/game server --> directory server (Directory Client Protocol)
Game clients and servers implement their respective portion of the directory server protocol.