Port 10573: Unassigned — One Of Thousands In The Empty Registry

What This Port Range Means

Port 10573 lives in the registered port range: 1024–49151. This range was created by the Internet standards committees as a public registry where any organization could request an officially-assigned port number for their service or application. It's the middle ground between the well-known system ports (0–1023) that have standard meanings, and the ephemeral ports (49152–65535) that operating systems assign temporarily to client connections.

In theory, the registered range is organized and maintained. In practice, it's mostly empty.

The Numbers

When RFC 6335 was written, approximately 9% of the registered port range was actually assigned. That means roughly 91% of ports between 1024 and 49151 have no official assignment. Port 10573 is part of that vast empty space. IANA doesn't even bother listing unassigned ports—there are too many. ¹

What You'll Actually Find

Port 10573 has no known official service. Searching the IANA port registry returns nothing. No protocol, no standard, no specification.

Unofficially, it could be used by any application. Some unassigned ports end up being claimed by ad-hoc services, custom applications, or legacy software that never bothered with official registration. Without monitoring your own network, you can't know if something on your system is using it.

How to Check What's Listening

If you want to know whether anything on your machine is actually using port 10573:

On Linux/macOS:

lsof -i :10573

On Windows:

netstat -ano | findstr 10573

Both commands show what process (if any) is listening. In most cases, the answer will be: nothing.

Why Unassigned Ports Matter

The fact that 91% of the registered port range is unassigned tells you something true about the Internet: we asked for too much. Someone created a 48,128-port registry expecting organizations would fill it with carefully-designed, officially-recognized services.

Instead, the Internet grew in a completely different direction. Applications claimed whatever port happened to work. Developers used unassigned ports rather than navigating IANA's registration process. Standards committees stopped caring about port numbers the way they used to.

Port 10573 is a reminder that the Internet we built doesn't always use the systems we designed for it. It's freedom and chaos layered on top of each other. ²

If something is legitimately running on port 10573 in your network, it's not because a standard said it should be. It's because someone made a decision, and it stuck.

Footnotes