There is a Yahoo Group (WinMXSoft) that has been trying to reverse engineer WinMX's 2.6 version protocol. A related SourceForge project has also been opened by one of the group members:
http://sourceforge.net/projects/openmx/
It's all still in early stages and the work is not necessarily too encouraging as WinMX has just upgraded to version 3.0 with a different WPNP protocol and of course may change its protocol again anytime in the future without warning.
- tg
