PortQry is a command-line utility developed by Microsoft that reports the port status of TCP and UDP ports on a local or remote computer. Unlike a simple Telnet test—which only tells you if a TCP connection succeeded—PortQry provides detailed information about the port’s state and can even query specific services to see how they respond. The Three States of a Port When you run PortQry, it returns one of three statuses: A process is listening on the target port. NOT LISTENING: No process is listening on the target port.
In the world of network troubleshooting, the ability to determine if a port is open, closed, or filtered is fundamental. While many administrators reach for heavy-duty tools like Nmap, Microsoft’s own remains one of the most lightweight, reliable, and "Windows-native" ways to diagnose connectivity issues. portqry
is a powerful, free command-line utility from Microsoft designed to help administrators troubleshoot TCP/IP connectivity issues. Unlike standard tools like telnet , which only report if a connection succeeded, PortQry provides a detailed analysis of a port's status and the service behind it. Core Functionality PortQry is a command-line utility developed by Microsoft
Testing UDP is notoriously difficult because it is a connectionless protocol. PortQry excels here by sending a formatted query to common UDP services (like DNS, SNMP, or RPC) and waiting to see if the service responds with data. 2. RPC Service Mapping NOT LISTENING: No process is listening on the target port
This is one of PortQry's most distinct features. In normal mode, a query happens once. In Test Mode ( -t ), PortQry continuously queries the target port until the user stops it (Ctrl+C). This is invaluable for: