When troubleshooting TCP/IP connectivity problems on a Windows XP system, you may want to find out what applications or services are listening on which open TCP and UDP ports. To make this task easier, Microsoft beefed up the Netstat command-line tool in Service Pack 2 with a new parameter.

The new -b parameter builds onto the information displayed by the -o parameter. The -b parameter allows the Netstat command to display the TCP or UDP port, the file names corresponding to the components of the service that owns the port, and the PID.

Then, you can use the Tasklist /SVC command to display the list of each service in each process. Now, cross reference the file name and the PID obtained from the Netstat -b command with the list generated by the Tasklist /SVC command to identify which services are currently using what ports.