What Range This Port Belongs To
Port 3601 falls in the registered ports range (1024–49151). These ports are assigned by IANA for specific applications and services. Unlike the well-known ports (0–1023), they don't require elevated privileges to open, and unlike the dynamic/ephemeral ports (49152–65535), they aren't handed out randomly to clients making outbound connections.
A registered port assignment is a reservation. Someone filed the paperwork with IANA, gave it a name, and it became theirs.
The Official Assignment: Visinet GUI
Port 3601 is registered on both TCP and UDP for a service called visinet-gui — "Visinet GUI." The registration dates to September 2002.1
That's nearly everything that's known. Searches for Visinet, Visinet GUI, and the registrant name return nothing useful. No company, no documentation, no surviving product. Whatever Visinet built — likely some kind of graphical management interface, given the name — it didn't outlast the early 2000s.
This isn't unusual. The registered port range is littered with software from companies that were acquired, folded, or simply stopped shipping. IANA doesn't reclaim ports when products die. The reservation sits on the books indefinitely.
Is Anything Actually Using It?
Port 3601 has no significant documented unofficial use. It doesn't appear in any major malware reports, doesn't show up as a common default for popular open-source software, and isn't associated with any framework or runtime that would make it recognizable in the wild.
If you see traffic on port 3601, it's worth investigating, but it's unlikely to be anything standard.
How to Check What's Listening
On Linux or macOS:
On Windows:
These commands show whether any process has opened port 3601 and what that process is.
Why Ghost Ports Matter
The registered port range has over 48,000 slots. Thousands of those registrations belong to products that no longer ship. Port 3601 is one of them.
This has a practical side effect: when developers need a port for internal tooling, services, or development environments, they often land on numbers that look unoccupied — and sometimes those numbers have a forgotten IANA entry. Port 3601 is available in practice, even if it isn't available on paper.
The real risk is the reverse: running something on a port that's technically assigned to something else can cause confusion in firewall rules, documentation, and incident response. Checking the IANA registry before settling on a port is a small step that prevents future headaches.
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