Port 32: Unassigned — A Gap in the Foundation

Port 32 is unassigned. No protocol has ever been registered to it. No RFC defines it. No service runs on it by convention. It is one of the original gaps in the well-known port range, empty since the earliest Assigned Numbers documents were published in the 1980s.¹

This is not an oversight. It is what a well-managed numbering system looks like.

The Well-Known Range

Port 32 falls within the system port range: ports 0 through 1,023. These are the well-known ports, reserved for services important enough to require special treatment.² On Unix-like operating systems, binding to any port in this range requires superuser privileges. You cannot casually claim a well-known port. It takes an act of the IETF or IESG to assign one.³

This makes the well-known range the most contested real estate in networking. There are only 1,024 of them, and new assignments face strict review. Port 32 has survived that entire history without anyone successfully arguing they needed it.

Its Neighbors

Port 32 sits between two protocols from the early Internet:

• Port 31: MSG Authentication, a protocol tied to the MSG messaging system¹
• Port 33: Display Support Protocol (DSP), assigned to Ed Cain¹

Both are relics. MSG Authentication is not in active use. The Display Support Protocol is a curiosity from an era when remote display was being reinvented in multiple ways simultaneously. Port 32 sits between two ghosts, and has always been the gap between them.

No Known Unofficial Uses

Unlike some unassigned ports that have been adopted by applications or targeted by malware, port 32 has no widely documented unofficial uses.⁴ No well-known trojans target it. No popular application has quietly claimed it. It is, by every measure available, genuinely quiet.

If you find something listening on port 32, pay attention. There is no standard reason for it to be open.

How to Check What Is Listening on Port 32

On macOS or Linux:

# Check if anything is listening on port 32
sudo lsof -i :32

# Or use ss (Linux)
sudo ss -tlnp | grep :32

# Or use netstat
sudo netstat -tlnp | grep :32

On Windows:

netstat -ano | findstr :32

If any of these return a result, investigate. An open well-known port with no assigned service is worth understanding.

Why Unassigned Ports Matter

The Internet's port numbering system works because it is not fully packed. The gaps are not waste. They are capacity. Every unassigned well-known port is a slot held in reserve for a future protocol important enough to earn a permanent, privileged address.

RFC 6335 makes this explicit: System Port assignments require documentation of why a Dynamic Port and a User Port are both insufficient.³ The bar is high by design. The well-known range is meant to be sparse, not full.

Port 32 is not nothing. It is an open seat, held for forty years, waiting for a protocol that has never arrived. That restraint is part of what makes the system work.