You dupe by tricking the server, You create a clone of the item or money server side.
Its done by packet editing most of the time, but alt 1 sucked enough to allow us to do it via memory for a while. The problem on their end was like No inter-server communication.
No ones just going to give you code to dupe that would destroy the game, if you some how manage to work it out dont release it public either it will kill the game. Same goes for anyone else reading this