Off and on I've been working on an input filter plugin for netplay.
There are some things to consider about this and Rice and I had a long winded conversation about it over a year ago (grin). I worked on it but found there to be no 'brilliantly' obvious solution to make it easy.
Kallisto support is the 'obvious' solution but it's slow because it's very generic.
The biggest problem is latancy and synchronization. It's possible to get 56K connections to be up to speed though with UDP or TCP. I think calling it a 'lan protocol' is kind of silly in perspective since the internet is composed of an androgenous combination of various physical media connections IE T1 DSL Dialup ethernet in 100T 100T/2 1000T 10T ATM you name it. Kallisto is pretty slow for netplay it probably has a lot of overhead I don't know what it's data burden is. my guess if if you have anything less than ISDN it will be slow.
Anyhow at least PJ64 recognizes my plugin

I just need it to link as both the graphics and input plugin and forward information between the emulator and the plugin. This is the point I stoped at basically

I'll probably get back to work on it sooner or later.
Cyb