One of the nicest features of the DB debugger family is the capability
for sending messages between the client program and the debugger
interface.  Unfortunately, this is not often used because many people
don't even realize it's available.  Used properly, this feature can be
an invaluable debugging tool.

The RDBMSG program demonstrates how you can send messages and/or
commands from the debugging stub in the Jaguar to the debugger interface
running on your computer.