Port 1573: itscomm-ns — The registered port that nobody remembers

Port 1573 lives in the strange middle ground of the Internet's port system. It has an official name—itscomm-ns—registered with IANA for both TCP and UDP. But if you search for documentation about what it actually does, you'll find almost nothing.¹²

This is more common than you might think.

The Registered Port Range

Port 1573 belongs to the registered ports range (1024-49151). These ports are assigned by IANA to specific services upon request. Unlike the well-known ports below 1024, which run fundamental Internet services, registered ports serve more specialized purposes—or at least they're supposed to.

The process works like this: an organization developing a network service can request a port number from IANA. They provide a service name, a description, and contact information. IANA assigns the port. The service goes into the registry.

And then... sometimes nothing happens.

What Is itscomm-ns?

Based on the service name, "itscomm-ns" likely stands for something like "ITS Communications Name Server" or "IT Systems Communication Name Service." The "-ns" suffix often indicates a name server or naming service component.

But that's speculation. The actual documentation—what problem this service solved, who created it, what protocol it speaks—has disappeared. The port exists in registries, but the service itself has left almost no trace.³

This doesn't mean port 1573 is unused. It means the original service either never gained adoption, was retired, or operates in environments so specialized that they don't generate public documentation.

The Reality of Port Assignments

The IANA port registry contains over 10,000 assigned ports. Most people will only ever encounter a few dozen of them. The rest exist in a kind of limbo—officially registered, technically available, practically forgotten.

Port 1573 is one of these ghosts. It has a name. It has an official assignment. But it doesn't have a story that survived.

What Might Be Using Port 1573

Just because the original service is obscure doesn't mean the port is empty. Any application can listen on any port above 1023 without special privileges. You might find:

• Custom internal applications that chose 1573 arbitrarily
• Legacy systems that once used itscomm-ns and still do
• Services that conflicted with the official assignment and used the port anyway
• Absolutely nothing

How to Check What's Using Port 1573

On your system, you can see if anything is listening on port 1573:

Linux/macOS:

sudo lsof -i :1573
# or
sudo netstat -tulpn | grep 1573

Windows:

netstat -ano | findstr :1573

If something is there, the output will show you what process owns it. If nothing appears, the port is unused—at least on your machine.

Why This Matters

Port 1573 represents something important about how the Internet works. Not every port carries vital traffic. Not every registered service becomes widely adopted. The port system is designed to accommodate both the handful of protocols everyone depends on and the thousands of specialized services that serve niche needs.

The registry isn't a catalog of what's actively used. It's a namespace—a way to prevent conflicts by giving everyone who needs a port number a unique place to claim.

Port 1573 claimed its place. Whether anything meaningful ever happened there is a different question.