Port 1083: Ansoft License Manager — A Registered Port That Became Obsolete

What This Port Was For

Port 1083 (both TCP and UDP) is officially registered with IANA for ansoft-lm-1—the Ansoft License Manager.¹² This was the licensing system for Ansoft HFSS, electromagnetic simulation software used by engineers designing antennas, circuit boards, and RF components.

The software needed to verify licenses before running. Port 1083 was the door where license requests arrived.

What Happened to It

Ansoft was acquired by Ansys. Starting with AnsysEM 2019 R2, the licensing mechanism changed. The separate Ansoft license files and license manager were consolidated into the unified Ansys License Manager, which uses different ports (typically port 1055 for FlexNet).³

Port 1083 wasn't officially deregistered. It just became unnecessary. The software that needed it evolved past it.

The Registered Port Range

Port 1083 sits in the registered port range (1024-49151). These ports are assigned by IANA to specific services when someone requests them. Unlike well-known ports (0-1023), which require root privileges to bind to, registered ports can be used by regular user processes.

When a company develops software that needs network communication, they can request a registered port. IANA assigns it. The port becomes associated with that service in documentation and firewall rules worldwide.

Then sometimes the service changes, or the company gets acquired, or the protocol gets replaced. The port assignment remains in the registry, but the actual traffic stops.

What This Port Represents

Port 1083 is an example of something common in the port registry: archaeological artifacts. Ports that once carried real traffic for real software, then became obsolete when the technology moved on.

The Internet is built on infrastructure that accumulates rather than replaces. Old assignments don't disappear. They just stop being used. Somewhere in a firewall rule or an old configuration file, port 1083 might still be listed as "Ansoft License Manager," even though the current version of the software hasn't used it in years.

How to Check What's Actually Using This Port

If you want to see what's listening on port 1083 on your system:

Linux/Mac:

sudo lsof -i :1083

Windows:

netstat -ano | findstr :1083

Most likely, nothing is. Unless you're running a very old version of Ansoft HFSS, or some other software happened to claim this port for unofficial use.

Why Unassigned and Obsolete Ports Matter

The port registry is like a historical record. It shows what protocols and services mattered enough for someone to request official assignment. Some of those services are still essential (HTTPS on 443, SSH on 22). Others, like port 1083, represent moments in time when specific software needed a specific door.

Understanding that ports can become obsolete is important for security. An old firewall rule allowing port 1083 because "that's the Ansoft license server" might still be in place years after the software stopped using it. That open port is now just an unused entry point—and unused entry points are security risks.

The registered port range is full of these ghosts. Officially assigned. Historically real. Presently irrelevant.

Port 1083 carried licensing requests for electromagnetic simulation software. Then the licensing system changed. The port remains registered. The traffic stopped.

That's how infrastructure works. The past doesn't get deleted. It just gets quietly ignored.