Port 662: PFTP — A Port Assignment That Doesn't Make Sense

Port 662 carries a peculiar distinction: it's officially assigned to a service that probably doesn't need it.

What PFTP Is

PFTP stands for "Preferred For Transfers"—an FTP client created in the mid-2000s with features like SSL/TLS support, server-to-server transfers (FXP), and directory synchronization.¹ It's registered with IANA under the contact Ben Schluricke.²

But here's the thing: PFTP is a client, not a server. FTP clients don't listen on ports waiting for connections. They initiate connections to FTP servers (typically on port 21 for control, port 20 for data). A client doesn't need a reserved port number.

The Unusual Assignment

Port 662 exists in the well-known range (0-1023), reserved for services assigned by IANA. These are ports where servers listen—SSH on 22, HTTP on 80, HTTPS on 443. Services that wait for the world to connect.

Port 662 was assigned to PFTP for both TCP and UDP. But an FTP client connecting to a remote server uses ephemeral ports (the high-numbered, temporary ports your operating system assigns on the fly). There's no reason for PFTP to listen on port 662.

This suggests either:

• The port was registered with a misunderstanding of how FTP clients work
• There was an intended server component that was never built
• The registration was made "just in case" and never utilized

What Actually Uses Port 662

In practice: probably nothing.

You can check what's listening on port 662 on your system:

Linux/macOS:

sudo lsof -i :662
# or
sudo netstat -tuln | grep 662

Windows:

netstat -ano | findstr :662

Chances are, you'll find nothing. This port sits in the registry, officially assigned, functionally dormant.

Why This Matters

Port 662 is a small reminder that the Internet's infrastructure isn't perfectly organized. The well-known port range is finite—only 1,024 numbers—and back when port assignments were more casual, some got claimed for questionable reasons.

Every unused assignment is a number that can't be reclaimed for something else. Port 662 is reserved forever for a client tool that doesn't need it, while other services squeeze into higher ranges or share ports through different protocols.

It's not a crisis. But it's a peculiarity. A footnote in the history of how the Internet's numbering system evolved—sometimes through careful design, sometimes through confusion, always permanently.

Checking Your System

If something is listening on port 662, it's not the official PFTP client. It could be:

• Malware using an obscure port to avoid detection
• Custom software that picked 662 arbitrarily
• A legitimate service running on a non-standard port

Always verify what's listening on your ports. Reserved doesn't mean secure.