WinMX

WinMX is a peer-to-peer file sharing program authored by Frontcode Technologies (http://www.frontcode.com/). WinMX began its life as an OpenNap client capable of connecting to several servers simultaneously, although Frontcode later , starting with WinMX 2, created a proprietary protocol, termed WinMX Peer Network Protocol (WPNP). WPNP version 2 was phased out as WinMX 3.0 and its WPNP version 3 protocol came into existence. Frontcode operates several cache servers to aid WPNP network operation.

Lopster (http://lopster.sourceforge.net/) used to have WPNP 2 support, although it was locked out with the arrival of WPNP 3.