Portqry is a command-line utility that you can use to help troubleshoot TCP/IP connectivity issues. The utility reports the port status of target Transition Control Protocol (TCP) and User Datagram Protocol (UDP) ports on a remote computer. You can run Portqry on Windows Server 2003, Windows 2000, and Windows XP.
http://support.microsoft.com/default.aspx?scid=kb;en-us;816103
