This does categorically not work - the aforementioned pirate World of Warcraft servers are ample demonstration that you cannot prevent piracy. There of course pirated copies of Diablo 3 in circulation. Tribes: Ascend proves that being free-to-play isn't even enough to prevent piracy.
This pretty much. There is no such thing as an unpirateable product, and that includes multiplayer games with dedicated servers whose source code has never been released (Tribes: Ascend and World of Warcraft both have pirate servers as an example). You need to learn to work assuming piracy is going to happen, and all the…