Maybe stacksmashing could help you reverse the link protocol, he's reverse engineered Tetris to the point its playable online via a server / special dongle he's made:
You might have already seen this, however it was only released a couple of weeks a go, so possibly not.
I'd certainly be interested in this, I always wanted to be able to link my GameBoy up to the PC and trade online as a kid, it would be great if that was finally possible!