Port 2258 is registered with IANA for the Rotorcraft Communications Test System (RCTS) — software used to test and align radio communications equipment on military helicopters and other rotorcraft. It supports both TCP and UDP. The registration was filed in August 2006 by Terry Eldridge.1
You will almost certainly never encounter this port in a general networking context. It exists for a narrow, specialized purpose: verifying that avionics radios work correctly before aircraft fly.
What Range This Port Belongs To
Port 2258 falls in the registered ports range (1024–49151). These ports are not reserved in the same way as well-known ports (0–1023), but they are tracked by IANA. Any organization or individual can apply to register a port for a specific service. Once registered, the assignment is listed in the IANA Service Name and Transport Protocol Port Number Registry.1
Registration does not mean enforcement. Nothing prevents another application from using port 2258 on your machine. It means only that IANA has recorded an intended use, and well-behaved software is expected to avoid conflicting with it.
What RCTS Actually Is
RCTS systems are hardware test sets — physical bench equipment used in military avionics maintenance. They test UHF and VHF radios, HAVE QUICK II tactical communications systems, and navigation equipment on military aircraft. Manufacturers like Aeroflex (now VIAVI Solutions) built these devices for the U.S. military and allied forces.2
The port registration suggests RCTS software communicates over a network — likely between the test set hardware and a controlling PC — using port 2258 for that connection.
Why Most Databases Call It Unassigned
Many third-party port reference sites are out of date or pull from incomplete snapshots of the IANA registry. Port 2258 is genuinely registered, but it's obscure enough that the registration gets missed. If you see it listed as "unassigned" elsewhere, those sources are wrong.
How to Check What's Listening on This Port
If you see activity on port 2258 and want to know what's using it:
On Linux or macOS:
On Windows:
Then match the process ID to a running application to identify the software.
Unless you work with military avionics test equipment, any process listening on port 2258 is using it for its own reasons — not RCTS.
Frequently Asked Questions
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