Port 328: Unassigned — A Reserved Space in the Well-Known Range

Port 328 is officially unassigned. It sits in the well-known ports range (0-1023) but has no service attached to it.¹

What This Means

The Internet Assigned Numbers Authority (IANA) divides port numbers into three ranges:

• Well-known ports (0-1023): Reserved for system services and widely-used protocols
• Registered ports (1024-49151): Available for user processes and less common services
• Dynamic/private ports (49152-65535): Used for temporary connections and private applications

Port 328 is in the first category. It's part of the exclusive range that requires IETF review or IESG approval to assign.² But despite being in this restricted space, no protocol has ever claimed it.

Why It's Unassigned

Not every port number in the well-known range has a purpose. The range 325-332 (which includes port 328) is marked "Unassigned" in the IANA registry.³ These ports exist as reserved space—numbers held back in case a future protocol needs them.

It's like keeping a row of seats empty at a theater. They're available, but nobody's sitting there yet.

Checking What's Listening

Even though port 328 has no official assignment, something on your system might still be using it. To check:

On Linux or macOS:

sudo lsof -i :328
# or
sudo netstat -tulpn | grep :328

On Windows:

netstat -ano | findstr :328

If these commands return nothing, port 328 is closed on your system.

Security Considerations

Unassigned ports have no inherent vulnerabilities—there's no service to exploit. But that also means:

• If something is listening on port 328, it's not standard behavior
• Firewalls typically block well-known ports by default unless explicitly opened
• Port scanners may probe port 328 as part of reconnaissance, but there's no known malware associated with it³

Why Unassigned Ports Matter

The existence of unassigned ports in the well-known range represents breathing room in the Internet's infrastructure. The architects of the port system didn't assign all 1024 well-known ports immediately because they understood something important: you can't predict what the network will need in 50 years.

Port 328 is insurance against future requirements. It's there if we need it.

Related Ports

Port 328 sits in a quiet neighborhood:

• Ports 325-327: Also unassigned
• Ports 329-332: Also unassigned
• Port 333: texar (Texar Security Port)
• Port 344: pdap (Prospero Data Access Protocol)