Basic Broadcaster (bb) allows you to simply transfer text messages from one computer to another on a LAN. The messages are broadcast in the LAN and and can be received by each machine running bb. No setup is required - simply start the application. Since bb is written in Java you'll need JRE version 1.6 or higher to run it.
Technically spoken UTF-8 encoded messages with a maximum size of 63KB are broadcast in UDP datagrams on port 4100 via IPv4 to the limited broadcast address. The messages are transmitted as plain text - no encryption or anything similar is done (!). As it is the nature of limited broadcasts, they are limited to the subnet in which the sending machine is located. (=> Your broadcasts will stay in your LAN and will not be forwarded to the internet.)
I decided to release bb under the terms of the GPL (although the source code lacks documentation).
Feedback and patches are welcome! Jan Murawski, firstname.lastname@example.org