(additionally Player 2 can then on the CLIENT setup a gamepad-to-keyboard mapping in order to use a gamepad) configure both Player 1 and Player 2 on DIFFERENT keys on the keyboard have the person on the SERVER use a gamepad and configure Player 2 to use the keyboard
So, in order to have 2 people play on the SERVER together you can Naturally, the SERVER computer doesn't know anything about any gamepads plugged into the CLIENT. You can then use the mouse or keyboard for input ON THE SERVER COMPUTER. The client logs into an existing session on a computer that is the server.
The way it works is like Windows Remote Desktop or VNC - you have a client and a server application. So if you still intent to do this (not recommended), you need to understand 2 very simple things: Obviously, this 3rd-party-program (and there's the first alarm bell ringing) is meant to give another person unrestricted access to your computer (2nd alarm bell ringing).