From the clients end, how would you do this? Or is it automatically done?
Client's end?
You don't even need that part. In fact, if you could put in a value for a Gameconnection on the client end then you could potentially abuse any server.
commandToServer('function name without ServerCmd',args, and, stuff);
For example, commandToServer('useTool',0); will pull out your hammer, and that number (7902 in your case) is automatically defined by the server, being the client that called the command.
Simplified:
Client does commandToServer('UseTool',0);
Server gets ServerCmdUseTool(7902,0);