Apple - Send short message to another Mac on the LAN

Messages app on Lion or Mountain Lion supports Bonjour discovery which lets computers discover other devices using Messages app on your local network without needing a central server setup.

Bonjour is not on by default, but you can find the option under Preferences, or simply ⌘+, to open up the panel. Select the account page, and you will find Bonjour in the sidebar.

Turn it on and you're good to go.

Now to retrieve the list of people on your local network, simply ⌘+1 to bring up the buddy list, it is also available under the Windows menu item.

You can also use netcat which is built into OSX and many *nix OSes to build a simple chat server:

On your first box (server) type the following in terminal:

nc -n -v -l 10001(or choose your own port here)

On your second box (client) type:

nc -n -v 192.168.10.1(IP address of first box) 10001(port chosen by first box)

Edit: -l and -p cannot be used together.

Try this:

• keep a text file you use for sending text in a folder on your desktop

• in Terminal run

  cat ~/Desktop/TRANSIT/this_message.txt |
      ssh user@remotehost "cat >> ~/Desktop/TRANSIT/this_message.txt"
  

You can then also create an automator action that watches the folder, TRANSIT in my example that executes the above bash command every time you drop a file in the folder...