Feb 192008

PortqryUI is GUI interface for portqry command line utility.This utility reports the port status of target TCP and User Datagram Protocol (UDP) ports on a local computer or on a remote computer. PortQry version 2.0 also provides detailed information about the local computer’s port usage.

Depending on the process that listens on a UDP port, sometimes it may be difficult to determine the status of that UDP port. When an unformatted zero-length or fixed-length message is sent to a target UDP port, the port may or may not respond. If the port responds, it has a status of LISTENING. If you receive an ICMP “Destination unreachable” message from a UDP port, or if a TCP reset response is returned from a TCP port, the port has a status of NOT LISTENING. Typical port scanning tools report that the port has a LISTENING status if the target UDP port does not return an ICMP “Destination unreachable” message. This result may not be accurate for one or both of the following reasons:

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