monitor the RS-232 port

I have a very different suggestion, and this is because I also work in the industry and no how many problems can be hidden inside communication chains.
Monitoring of communications with hardware is very common. You probably want to spy on RS-232, and this can be extremely useful if you want to reverse engineer communications performed by software/firmware not accessible to you. That's why I voted "5" for your question. (I almost forgot, there is an application to monitor it: please see my other answer.)

However, in case you want to monitor your own software, you need to embed a tool for optional monitoring permanently into you low-level communication functions. I think, this is your case, because you mention inconvenience in debugging, but you did not say it is impossible. One of the best and non-intrusive ways of monitoring without debugger is writing to the system event log.

For a more advanced example, I recently developed a framework for development of Windows Services through the application working in dual-mode: as a Windows Service and a GUI (additionally, as a service installer). So the options could separately switch on/off logging in the UI control or System event log on different level of verbosity. If you create such a fundamental tooling for all your communications, it will pay off later because of massive diagnostics/debugging problems you may face down the road, I'll guarantee that.

Good luck,

—SA