xmessage origin
 

How can I find out from where (which machine)
the xmessages I get on my machine are coming?
(I know how to prevent it, I want to know which
machine on internal LAN is sending them if I
have allowed many machines, by using xhost +.)

You can use:

# netstat -a

and

search for a line like:

tcp 0 0 <your machine>:6000 <the machine you want to find out>:1033 ESTABLISHED

Hope that helps ...

Thanks for reply vladkrack.
But I found follwing is superior:
xlsclients -display <my IP address>:0.0
It directly gives name and IP of machine posting xmessage, including the command that invoked xmessage.