Monitoring X Traffic with xmon on Ubuntu

• Monitoring X Traffic with xmon on Ubuntu is quite a challenge. xmon is basically a tcp/ip listener (you could have it listen to your SMTP traffic instead, if you wanted) and Ubuntu X servers by default don't listen to tcp ports (only to a unix socket).
• To listen to the traffic anyway, open up a terminal and start a second X server on display :2
  sudo -s
  X :2 &
  Then, in that same terminal, or in another terminal with sudo, start xmond and let it connect to the new server you just started:
  xmonui | xmond -server localhost:2 -port 0
  Now start (in a new terminal) the application you want to monitor on the correct display:
  DISPLAY=localhost:1
  export DISPLAY
  start-your-app