Slackware :: Broadcast Messages From Server To Clients

I am searching for a way to broadcast a simple message from a server to the other machines (clients) on my local network every day at 22:30 (10:30pm) to warn users that the server will shutdown in 30 minutes (energy saving strategy). Basically, I was thinking to add a cron entry ion the server crontab to do so. before I go ahead with that, I tried several ways to accomplish this action. Then I tried simply "wall" and got a text promt to type in my message. At the end I pressed CTRL+D and got a popup displaying my message. So it worked but it was on the server's monitor. How can I send this message to a remote machine? Is wall the proper command to do so?

I also tried using paswordless ssh..It doesnt work. Basically I can login on the remote machine using passwordless ssh but when I issue either kdialog or xmessage, I get error "cannot connect to X server on diaplay 0:0" (or something similar).I tried also ssh 'wall 'message'' but it also says "cannot connect to X server on diaplay 0:0"So far I have several ways but nothing really works..There must be a real way to to that?All machines are Slackware 13.1 based.