Serial port software

[HDowns]

I need to watch the commands and bytes being sent back and forth. On Windows I have used this application in the past: Serial Port Monitor. I need
something that does the same on Linux. It must be able to run on the same machine that is running the application that uses the port. After searching a lot of Linux apps that purport to do this, I can’t find any that will actually do it. Any ideas?
--
Helen