Port 2686: Registered but Silent

What Range This Port Belongs To

Port 2686 falls in the registered port range (1024–49151), sometimes called "user ports." ¹

These ports are different from the well-known ports (0–1023) that belong to foundational protocols like HTTP, SSH, and DNS. Registered ports don't require system privileges to use, and IANA maintains a registry of official assignments to prevent collisions between applications. The range is large enough that thousands of entries exist — some famous, most obscure.

What IANA Says

Port 2686 is not unassigned. The IANA registry lists it under the service name mpnjsomg, registered to Takenori Miyahara at pfu.co.jp. ²

PFU is a Japanese technology company, long a subsidiary of Fujitsu and now part of Ricoh, best known for making document scanners — the ScanSnap line. What "mpnjsomg" stands for, or what network function it serves, is not documented anywhere publicly. No RFC. No product documentation. No forum thread where someone figured it out. The registration exists, the name exists, and that's where the trail ends.

This is not unusual in the registered range. Companies and developers have registered ports for internal protocols that were never described in public specifications, or for products that were discontinued before documentation reached the Internet.

Known Unofficial Uses

None documented. Port 2686 does not appear in security advisories, does not appear in malware databases, and does not appear in any notable software configurations. It is quiet.

How to Check What's Listening on This Port

If port 2686 is open on a machine you control, a few commands will tell you what's using it:

Linux / macOS:

# Show the process listening on port 2686
sudo lsof -i :2686

# Or with ss (Linux):
sudo ss -tlnp | grep 2686

Windows:

netstat -aon | findstr :2686

The PID from these commands can then be looked up in your process manager or with tasklist (Windows) / ps (Linux/macOS) to identify the application.

Why Unassigned (and Undocumented) Ports Matter

The registered port range functions as a coordination layer. When an application claims a port number, it's making a request to be predictable — operators can configure firewalls, monitoring tools can build expectations, and users can know what to expect.

When a port is registered but undocumented, it creates a small gap in that coordination. Something claimed it. But you can't know what "something" is from the outside, which means you can't make an informed decision about whether to allow or block it.

Port 2686 is an example of a port that technically has an owner, but practically behaves like it doesn't. If you see it active on a system, the right response is to investigate — the commands above will tell you what's actually there.