Example: Querying a port with no service bound to it. UDP port 137 is NOT LISTENING
UDP port 53 (domain service): LISTENING
The port is open but the application doesn't respond to the specific packet sent. A firewall is silently dropping the packet. Advanced Troubleshooting Features
PortQry is a command-line utility used to query the status of TCP and UDP ports on a local or remote computer. In this essay, we will focus on the UDP (User Datagram Protocol) functionality of PortQry. UDP is a transport-layer protocol that provides best-effort delivery of data between devices on a network. It is commonly used for applications that require fast and efficient communication, such as online gaming, streaming, and VoIP (Voice over Internet Protocol). portqry udp
portqry.exe -n <IP_Address> -p udp -e <Port_Number>
Unlike TCP, UDP is — no handshake, no ACK. So portqry can’t just “connect” to a UDP port to see if it’s listening.
portqry.exe -n 192.168.1.10 -p udp -r 500:510 Example: Querying a port with no service bound to it
To query a UDP port, you must use the -p UDP switch. By default, PortQry uses TCP if this is not specified.
portqry.exe -n 192.168.1.10 -p udp -o 53,161,67
PortQry UDP is a feature of the PortQry utility that allows users to query the status of UDP ports on a computer. With PortQry UDP, users can determine whether a specific UDP port is open, closed, or filtered on a local or remote computer. This can be useful for troubleshooting network connectivity issues, testing firewall configurations, and identifying potential security vulnerabilities. It is commonly used for applications that require
Or with a host that sends ICMP unreachable:
When troubleshooting network connectivity, the first tool most administrators reach for is telnet or Test-NetConnection (PowerShell). While these are excellent for TCP ports, they often fall short when testing User Datagram Protocol (UDP) services. Because UDP is connectionless, testing it requires a specialized approach.
, a Microsoft command-line tool, to troubleshoot UDP connectivity. Overview of PortQry UDP Logic Unlike TCP, which uses a three-way handshake, UDP is connectionless. When PortQry sends a UDP packet, it determines the status based on the response (or lack thereof): LISTENING: The target sent a specific application-level response. NOT LISTENING: The target sent an "ICMP Destination Unreachable" message. FILTERED: No response was received. This often indicates a firewall is blocking the traffic. Avigilon Support Community Basic Command Syntax To query a single UDP port, use the following structure in your command prompt: