What Port 3720 Is
Port 3720 is registered with IANA under the service name ufastro-instr, short for "UF Astro. Instr. Services" — the University of Florida Department of Astronomy's instrument control services. The registration covers both TCP and UDP, and dates to March 2003.1
The contact on the registration is David B. Hon.
That's essentially everything officially known about this port.
What This Port Range Means
Port 3720 sits in the registered ports range (1024–49151). These ports are assigned by IANA to specific services upon request — but assignment doesn't mean use. Anyone can submit a registration. IANA doesn't verify that the software ships, that the port is actively used, or that the service ever ran outside the registrant's own lab.
The registered range exists to prevent collisions: if your telescope control software registers port 3720, nobody else is supposed to use it for something conflicting. In practice, the tens of thousands of registered ports include many entries like this one — niche academic or enterprise software that registered a port, then quietly disappeared into history.
Does Anything Actually Use This Port?
Almost certainly not on the public Internet. This kind of registration — academic instrumentation, mid-2000s, no public documentation — describes software that likely ran on a private campus network, controlled a spectrograph or detector array, and never needed to traverse the open Internet at all.
Port databases and security scanners show no meaningful traffic patterns on port 3720.2
If you're seeing activity on this port on your network, it's worth investigating. Obscure registered ports sometimes get repurposed by:
- Custom enterprise or research software
- Game servers that pick ports informally
- Malware or remote access tools avoiding well-known ports
How to Check What's Listening on This Port
On Linux or macOS:
On Windows:
The process ID in the output will tell you exactly what's listening. Cross-reference it against your process list and you'll have your answer.
To check remotely (with appropriate permission):
Why Entries Like This Matter
The registered ports list is a record of intent. It captures the moment when someone built something specific enough to deserve a port number. Most of those services are long gone — the software unmaintained, the servers decommissioned, the registrants moved on. What remains is an entry in a text file and, occasionally, a port that nobody uses but nobody reassigns either.
Port 3720 is one of those. A telescope got a number. Time passed.
Frequently Asked Questions
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