Sorry for the cryptic weird title...

I wonder how can I play in multiplayer whn both instances running on same computer (127.0.0.1).
Am I missing something or there's some trick to focus both windows separately at the same tome?
I mean configure JOY1 (as Player1) and bind its inputs focusing with master window and configure JOY2 (as Player2) to bind its inputs focusing with slave window having the two instances both on focus.