Port 2747: fjippol-swrly — Fujitsu's Ghost Protocol

What This Port Is

Port 2747 sits in the registered port range (1024–49151) and carries an IANA assignment: fjippol-swrly, registered by Fujitsu.

That assignment tells you almost nothing. There is no RFC, no public protocol specification, and no documented use of this service outside internal Fujitsu systems. The contact on file is tatibana&yk.fujitsu.co.jp — a Fujitsu engineer who registered a block of five consecutive ports sometime in the 1990s and left no further trail.

The fjippol Block

Ports 2747 through 2751 are all registered as fjippol variants:¹

The "fji" prefix almost certainly stands for Fujitsu Japan Internal. "Ppol" likely means polling. Beyond that — what swrly means, what these services actually exchange, whether they ever ran in production — is unknown. This is a proprietary protocol that was never opened up.

What the Registered Range Means

The registered port range exists for exactly this kind of thing: software vendors and organizations that need a consistent port for their applications can register one with IANA. Unlike well-known ports (0–1023), registered ports don't require root or administrator privileges to open, and there's no strong enforcement of what actually runs on them.

The result is a range full of legitimate services, abandoned registrations, and de facto standards that were never formally registered. Port 2747 is firmly in the "registered but effectively dormant" category.

If you find port 2747 open on a system you didn't configure, the Fujitsu polling service is almost certainly not the explanation. Something else is listening there.

How to Check What's Actually Listening

On Linux/macOS:

# Show what process has port 2747 open
ss -tlnp | grep 2747
# or
lsof -i :2747

On Windows:

netstat -ano | findstr :2747

The PID from netstat can be cross-referenced in Task Manager or with:

tasklist | findstr <PID>

Should You Be Concerned?

Port 2747 has no known malware association, no CVEs tied to it, and no documented exploit history. If something is listening on this port unexpectedly, the concern is the same as any unexpected open port: find out what it is, verify it's legitimate, and close it if it isn't.

Unrecognized open ports aren't automatically dangerous. They are always worth understanding.