nx-x11proto-core-dev - 2:3.5.99.26-2 main

NX is a software suite which implements very efficient
compression of the X11 protocol. This increases performance when
using X applications over a network, especially a slow one.
.
This package provides development headers describing the wire protocol
for the core nx-X11 protocol, and also provides a number of utility headers,
used to abstract OS-specific functions.