Port 207: AppleTalk Unused — A Reserved Space That Never Was

What Port 207 Is

Port 207 (both TCP and UDP) is officially registered with IANA as "at-7" (AppleTalk Unused).¹ It sits in the well-known port range (0-1023), the System Ports that require privileged access on most operating systems.

But here's the thing: it was never used. Not once. Not ever.

The AppleTalk Story

In 1985, Apple released AppleTalk — a proprietary networking protocol that made connecting Macintosh computers genuinely plug-and-play.² In an era when network configuration required manual intervention, AppleTalk offered automatic address assignment, distributed name services, and self-configuring routing. By 1987, it was the most-used networking system in the world, with over 130,000 networks installed.²

Apple reserved ports 201-208 for AppleTalk services:¹

• Port 201: AppleTalk Routing Maintenance (at-rtmp)
• Port 202: AppleTalk Name Binding (at-nbp)
• Port 203: AppleTalk Unused (at-3)
• Port 204: AppleTalk Echo (at-echo)
• Port 205: AppleTalk Unused (at-5)
• Port 206: AppleTalk Zone Information (at-zis)
• Port 207: AppleTalk Unused (at-7)
• Port 208: AppleTalk Unused (at-8)

Four of those eight ports — including port 207 — were marked "unused." Reserved but unassigned. Held for services that were planned, or imagined, or just... never built.

The Decline

TCP/IP won. The Internet's protocol suite proved more flexible, more open, more universal than any proprietary alternative. By the 1990s, AppleTalk's dominance faded. Apple officially dropped support in Mac OS X v10.6, released in 2009.²

AppleTalk is dead. But port 207 remains.

What This Port Means

Port 207 represents something strange in the Internet's architecture: permanent reservation for a deprecated protocol. IANA generally doesn't reassign port numbers that have been de-assigned until all unassigned ports in a range have been allocated.³ Port 207 sits in the well-known range — valuable real estate in the port number space — reserved for a service that never existed in a protocol that no longer runs.

It's a fossil. A marker of a different era in networking history.

Security Note

Because port 207 has no active service, any traffic on this port should be investigated. Some historical reports indicate malware has used port 207 for communication.⁴ If you see unexpected traffic on this port, it's not AppleTalk — it's something else, and it probably shouldn't be there.

How to Check What's Listening

On Unix-like systems (Linux, macOS):

# See what's listening on port 207
sudo lsof -i :207
sudo netstat -an | grep 207

On Windows:

# Check port 207 status
netstat -an | findstr :207

If nothing appears, the port is unused — which is exactly what it was designed for.

Why Unused Ports Matter

The Internet's port system is finite. The well-known range has only 1,024 ports. Every unused reservation is space that can't be allocated to new services. Port 207 and its unused siblings (203, 205, 208) occupy four slots in this constrained space, held for a protocol that will never return.

IANA's conservative approach makes sense — reassigning ports risks breaking old systems that might still reference these numbers. But it creates a permanent archaeological layer in the port registry: numbers reserved for technologies that no longer exist, services that were never built, protocols that lost the standards war.

Port 207 is one of these ghosts. A number with a name but no function. A placeholder that became permanent.