Port 577: vnas — The ghost in the registry

Port 577 sits in the well-known ports range with an official assignment to a service called "vnas," but here's the strange thing: nobody seems to know what vnas actually does.

What We Know

Port 577 is assigned to vnas for both TCP and UDP protocols.¹ The assignment is official—it's in the IANA registry, the authoritative record of every port assignment on the Internet. But that's where the trail goes cold.

There's no RFC documenting the protocol. No specification explaining what vnas stands for or what problem it was meant to solve. No active deployments that anyone talks about. Just a name in a registry and a port number reserved decades ago.

The Well-Known Range

Port 577 lives in the well-known ports range (0-1023), which means it was assigned by IANA under strict procedures. These ports are reserved for system services—protocols important enough to need a permanent, globally recognized address.

Getting a port in this range requires IETF review or IESG approval.² Somebody, at some point, believed vnas was important enough to deserve this permanent reservation. But whatever vnas was, it didn't survive.

Ghost Ports

The Internet is full of ports like this. Services that were assigned in the 1980s or 1990s, used briefly or never deployed widely, then abandoned as technology moved on. But the port reservations remain. The registry is a tombstone garden—hundreds of names that meant something to someone, once.

Some ghost ports have fascinating histories if you dig deep enough. Others, like 577, have erased themselves so completely that even their purpose is forgotten.

Checking What's Listening

If you want to see if anything is actually using port 577 on your system, you can check:

On Linux/macOS:

sudo lsof -i :577
sudo netstat -tulpn | grep :577

On Windows:

netstat -ano | findstr :577

You'll probably find nothing. Port 577 is almost certainly silent on your machine—a reserved address with no service to answer it.

Why Keep Dead Assignments?

You might wonder why IANA doesn't reclaim these abandoned ports. The answer is caution. What if vnas is still running somewhere, on some critical system nobody remembers? What if reassigning the port breaks something that's been working quietly for 30 years?

The Internet is built on the assumption that port numbers don't change. Once assigned, they stay assigned. Even when the service dies and the documentation disappears and nobody can remember what the acronym stood for.

Port 577 is a ghost. But it's a ghost with a permanent address.