Port 189: Queued File Transport — The Empty Queue

Port 189 sits in the well-known ports range (0-1023), reserved by the Internet Assigned Numbers Authority for standardized services. It was officially assigned to Queued File Transport (qft), a store-and-forward protocol designed for an era when file transfers needed to wait their turn.¹

What Queued File Transport Was

Queued File Transport was exactly what its name suggests: a protocol that queued file transfers and handled them in sequence. When networks were slower and more precious, you couldn't just blast files across the wire whenever you wanted. You queued them. The system handled them one by one.²

The protocol was documented for Cray supercomputers in 1990. That tells you the world it came from—mainframes, controlled environments, systems where every network operation was deliberate and managed.

The World That Needed Queues

Before the web existed, file transfers were expensive operations. Bandwidth was measured in kilobits. Network time was allocated. A large file transfer could monopolize a connection that other users needed.

So you queued them. The protocol would accept your file transfer request, put it in line, and process it when resources were available. Store-and-forward. Simple. Practical.

This made sense in 1990. It makes no sense now.

What Happened

The world changed. Networks got faster. Bandwidth got cheaper. The entire concept of queueing file transfers at the protocol level became obsolete. You can send files whenever you want now. The network handles it.

Port 189 is still registered to qft in the IANA database, but the protocol is dead. No modern system implements it. No traffic uses this port for its intended purpose.

The Well-Known Ports Range

Port 189 occupies space in the well-known ports range—the first 1,024 ports that IANA assigns to standardized protocols. These were meant to be the foundation: the services that every system needed.

Some of them still are. SSH on port 22. HTTPS on port 443. DNS on port 53. These ports carry the Internet.

Others, like port 189, are archaeological sites. They mark protocols that mattered once and don't anymore.

Checking What's Listening

On Unix-like systems, check what's listening on port 189:

# See if anything is listening
sudo lsof -i :189

# Or with netstat
sudo netstat -tulpn | grep :189

# Or with ss
sudo ss -tulpn | grep :189

On Windows:

netstat -ano | findstr :189

You'll almost certainly find nothing. This port is quiet.

Why Unassigned Space Matters

Port 189 isn't technically unassigned—it has an official registration. But it's functionally abandoned. The protocol it was assigned to doesn't exist in practice anymore.

The well-known ports range is finite. Only 1,024 ports. Each one assigned to qft is one that can't be assigned to something current and useful. The IANA doesn't revoke assignments lightly, so these ghost protocols remain registered, occupying space in a namespace that can never grow.

This is the digital equivalent of a graveyard. The names remain. The services are gone.

The Empty Queue

Queued File Transfer solved a real problem in 1990. Networks were slow. Resources were scarce. Queueing made sense.

Thirty-five years later, the problem doesn't exist. Port 189 was built for a world where file transfers needed to wait their turn. That world is gone. The queue is empty. It will stay empty.