Home Office Network

Troubleshoot TCP/IP connectivity (check TCP and UDP port status)

Portqry.exe command-line utility:

Portqry.exe is a command-line utility that you can use to help troubleshoot TCP/IP connectivity issues.(check the TCP port status) Portqry.exe runs on Windows computers. The utility reports the port status of TCP and UDP ports on a computer that you select.

The port status is as following:

*Listening (open)

A process is listening on the port on the computer that you selected. Portqry.exe received a response from the port.
For example, you have web server is running on target computer, the web server is listing the TCP port 80.

*Not Listening (close)

No process is listening on the target port on the target system. Portqry.exe received an Internet Control Message Protocol (ICMP) “Destination Unreachable - Port Unreachable” message back from the target UDP port. Or if the target port is a TCP port, Portqry received a TCP acknowledgement packet with the Reset flag set.

*Filtered

The port on the computer that you selected is being filtered. Portqry.exe did not receive a response from the port. A process may or may not be listening on the port.

This utility also has a Windows application with GUI, which you can use easily without typing command line dos command.

The following shows the result to check the yahoo.com ’s web server port 80 status :

TCP/IP Network FAQ