Portmon is an application that lets you monitor serial and parallel activity on your local system, or any computer on the network that you can reach via TCP/IP. It is the most powerful tool available for tracking down port-related configuration problems and analyzing application port usage.
Portmon works on Windows NT 4.0, Windows 2000, Windows 95 and Windows 98. Note: if you want to run Portmon on Windows 95 you must install the WinSock2 update, available for free download from Microsoft抯 Web site.