Note: The log information produced by this tool can be difficult to understand if you don't have a good knowledge of the TCP/IP network protocols.
Microsoft has released a program called PORTQRY.EXE, which is a tool designed to check TCP/IP network connectivity and port status (both TCP and UDP) on local or remote computers . If you're any type of system administrator (such as: e-mail, database, web, etc.), then you will need a utility like this in your diagnostic tools arsenal.
This program was originally included as part of the Microsoft Windows Server 2003 Support Tools. Since then Microsoft has released a new version of it (called PORTQRYV2.EXE) that includes new features and functionality not available in the earlier version.
PORTQRYV2.EXE is a command-line utility, so to get the syntax to run it or to see examples of the output go to the following Microsoft Knowledge Base Article (MSKB).