I'm working on a software development project that requires me to send signals to a device via an RS-232 port. Sadly the included utilities for transferring to and from the device would not work for mass distribution, so I'm left to writing my own. The included documentation doesn't really give any examples of the device's packet structure, and I would like to examine the packets sent to and from their included software package.

Is there a good program that would allow me to monitor packets coming to and from the serial port? Free is preferred, but not required.

  • 4
    serial port communications traditionally don't use "packets" (like ethernet or USB data transmissions). tho that's not to say a modern serial port application couldn't layer a packet scheme on top of more traditional serial transmissions for its own purposes. Jan 28, 2010 at 17:36
  • @~quack - The device I am using does use a packet scheme, though I didn't realize that isn't something inherent to serial port communications. This is all a bit new to me.
    – user17909
    Jan 28, 2010 at 17:50
  • welcome to the wonderful world of device programming... :) Jan 28, 2010 at 18:11

2 Answers 2


Portmon, from Sysinternals, will do what you need:

Portmon is a utility that monitors and displays all serial and parallel port activity on a system. It has advanced filtering and search capabilities that make it a powerful tool for exploring the way Windows works, seeing how applications use ports, or tracking down problems in system or application configurations.

enter image description here

  • Yes! This does exactly what I wanted! Thanks. :)
    – user17909
    Jan 28, 2010 at 18:59
  • I don't think Portmon works on newer versions of 64-bit Windows (Windows Vista and later?). Apr 6, 2018 at 16:16

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy