What Port 2687 Is
Port 2687 is officially registered with IANA1 under the name pq-lic-mgmt — the license management service for PQ Systems, a company that makes statistical process control (SPC) and gage management software used in manufacturing quality assurance.
If you have never worked in a factory or manufacturing quality lab, you have probably never encountered this port. That is expected.
What PQ Systems License Manager Does
PQ Systems sells software like CHARTrunner and GAGEpack to help manufacturers track defects, measure process variation, and manage calibration equipment. Their concurrent-user licensing model lets a company buy a fixed number of seats rather than per-workstation licenses.
The license manager runs as a Windows service on one computer inside the company network. When any PQ software starts on a workstation, it reaches out to that server on port 2687 to ask: is a license available? If yes, the seat is granted and the software opens. When the user closes the software, the seat is released.2
It is a short, transactional conversation: "Can I run?" / "Yes, go ahead" — or "No, all seats are taken."
The Registered Ports Range
Port 2687 sits in the registered ports range: 1024–49151.
This range is managed by IANA. Anyone can apply to register a port for a specific service, and IANA records it so that different software does not accidentally collide. Unlike the well-known ports (0–1023), registered ports do not require administrator privileges to open on most operating systems.
The range has 48,128 slots. Most of them are quietly occupied by software you have never heard of, doing things that keep specific industries running. Port 2687 is a good example of this: invisible to most people, essential to the engineers who depend on it.
Security Notes
Port 2687 has no notable security history. It is not associated with common exploits or attack tools. If you see unexpected traffic on this port and you are not running PQ Systems software, it is worth investigating, but there is no particular reason for concern on its own.
Firewall rules for PQ Systems installations typically need to allow TCP traffic on port 2687 between client workstations and the license server.
How to Check What Is Listening on This Port
If you want to see whether anything is bound to port 2687 on your machine:
macOS / Linux:
Windows:
The output will show the process ID. On Windows, you can look up the process in Task Manager. On macOS/Linux, lsof includes the process name directly.
Related Ports
Port 2764 is the primary port used by PQ Systems License Manager. Port 2687 is the secondary port in configurations that use both.3
Frequently Asked Questions
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