XMX is an X protocol multiplexor.  It is a standalone utility for displaying
an X Windows session on multiple displays.  XMX takes advantage of the
networked nature of the X Window System by tapping the communication link
between an X client and an X server.  In this way, XMX works with any
X clients and any X servers, without the need to modify either.

It's tempting to call this "broadcast software," and that is certainly the
effect.  In reality, though, XMX is "multicast" software.  It must know
all the slave machines ahead of time and it connects to each one directly.
XMX is more like mail than news.

XMX connects to N servers like an X client, then accepts connections from
M clients like an X server.  One of those servers is designated the "master"
from which input is directed to the clients.  The other servers are "slaves."
Slave servers receive only those protocol requests that are necessary for
them to maintain a visual look-alike of the master server's display.

This software was developed at Brown University for use in our electronic
classroom.  Some version of it has been in use here since 1988.