Description of problem:

  I have one (main) ThinkPad which runs the X11 clients for an external XServer.
By default, tpb displays its OSD also on this other XServer, which makes no sense.

Version-Release number of selected component (if applicable):

  tpb-0.6.4-3.fc5

How reproducible:

  Every time.

Steps to Reproduce:
0. Find a ThinkPad with gdm and tpb.
1. Setup gdm to allow xdmcp.
2. Setup firewall to allow network access from external X11 server.
3. Start X11 server on another box.
4. Press the "change display brightness" or "change sound volume" buttons on the
main ThinkPad.
  
Actual results:

  The "Brightness" or "Volume" tpb OSD will now show on *all* connected XServers.
Expected results:

  The tpb OSD should show only on the XServer running on the main ThinkPad.
After all, the tpc OSD only displays the status of the main ThinkPad, and
nothing else.

Additional info:

My new, working /etc/X11/xinit/xinitrc.d/tpb.sh, which makes the tpb OSD show
only on the main ThinkPad (on all XServers actually running on that hardware),
but not on any external XServers:

#!/bin/sh
if echo "$DISPLAY" | grep "^:" > /dev/null; then
        /usr/bin/tpb -d
fi

This uses the fact that local DISPLAYs are something like ":0", ":0.0", ":1.1",
whereas external DISPLAYs are something like "192.168.15.35:0" or
"host.name.local:1".