Port 2659: Unassigned — A Gap in the Registry

What This Port Is

Port 2659 is unassigned. IANA — the organization that maintains the official registry of port number assignments — has not allocated this port to any service or protocol.¹

It sits in the registered port range: 1024 through 49151. Ports in this range are neither the famous well-known ports (0–1023, reserved for foundational protocols like HTTP, DNS, and SSH) nor the ephemeral ports (49152–65535) that operating systems assign dynamically to outgoing connections. Registered ports are supposed to be claimed by applications and services that request assignment. Many never are.

Any Known Unofficial Uses

Security databases note that some unspecified malware has used port 2659 at some point — but this is a thin claim. Threat actors routinely use arbitrary high-numbered ports for command-and-control traffic precisely because those ports are unmonitored and unrecognized. Finding a port number in a "suspicious ports" list without a specific named trojan attached tells you more about how security databases are built than about port 2659 itself.²

There is no widely observed legitimate application that runs on this port. No software package, no protocol specification, no open-source project is known to default to 2659.

How to Check What's Listening

If you see traffic on port 2659 and want to know the source:

On Linux/macOS:

# Show which process is listening on port 2659
sudo ss -tlnp | grep 2659
# or
sudo lsof -i :2659

On Windows:

netstat -ano | findstr :2659

The process ID in the output can be matched against Task Manager or tasklist to identify the owning application.

If something is listening on this port and you don't recognize it, that's worth investigating — not because port 2659 is inherently suspicious, but because unexpected listeners on any port deserve an explanation.

Why Unassigned Ports Exist

The registered range contains 48,128 possible ports. IANA has assigned roughly 10,000–15,000 of them over the decades. The rest — like 2659 — exist as potential space: available if an application needs a standardized home, unclaimed until someone asks.

This gap isn't a flaw. It's headroom. The port system was designed with the assumption that new protocols would keep arriving, and they have. The unassigned ports are the empty shelves in the registry, waiting.