Port 2137: "connect" — Registered, Undocumented

Port 2137 lives in the registered port range (1024–49151). IANA has assigned it. Someone claimed it. And then, apparently, nothing happened.

What IANA Says

The IANA Service Name and Transport Protocol Port Number Registry lists port 2137 as assigned to a service named "connect" on both TCP and UDP, registered by Reid Ligon at connectrf.com. The "RF" in that domain suggests radio frequency technology — possibly some kind of RF device connectivity protocol.

Beyond the registrant's name and email, the public record is blank. No RFC. No specification. No documentation anyone can find. Whatever "connect" was meant to do, it never became a thing people use or write about.

This is more common than you'd expect. The registered port range contains thousands of ports claimed by projects and companies that never gained traction, were abandoned, or simply never needed the public registration they applied for.

What the Registered Port Range Means

Ports 1024–49151 are the registered ports. Unlike the well-known ports (0–1023), you don't need root or administrator privileges to bind to them. Any application can open a server on port 2137 without special permissions.

IANA maintains registrations in this range to prevent collisions — so two different software projects don't accidentally pick the same port and confuse administrators. But registration is not enforcement. There's no technical mechanism stopping any software from using any port. The registry is a coordination system, not a lock.

What's Actually on Port 2137

Nothing standard. If you see traffic on port 2137 on your network, it's not the obscure "connect" service — it's whatever local software chose that port, whether by design or at random.

To check what's using port 2137 on a machine:

# Linux/macOS — show what process is listening on port 2137
ss -tlnp | grep 2137
# or
lsof -i :2137

# Windows
netstat -ano | findstr :2137

If something shows up, the process ID will point you to the actual application.

A Note on the Number

2137 is a famous number on the Polish Internet — a meme tied to the time of death of Pope John Paul II (21:37) that became a vehicle for dark humor and cultural critique in Polish online communities.¹ It has nothing to do with networking. But if you ever wonder why a Polish developer named their test server's port 2137, now you know.

• IANA Service Name and Transport Protocol Port Number Registry — Port 2137
• SpeedGuide: Port 2137
• RFC 6335: IANA Procedures for the Management of the Service Name and Port Number Registry