Port 890: Unassigned — The ghost of NetInfo

Port 890 sits in the well-known port range (0-1023), the territory normally reserved for fundamental Internet services assigned by the Internet Assigned Numbers Authority (IANA). But when you check the official registry, port 890 isn't there.¹

Yet search for port 890 in any port database and you'll find it listed as "NetInfo" or "Mac OS X RPC-based services."² What's happening here is a glimpse into how the Internet remembers things that no longer exist.

The Well-Known Range

Ports 0-1023 are called well-known ports or system ports. These require root privileges to bind to on Unix-like systems. They're meant for essential services—HTTP on 80, HTTPS on 443, DNS on 53.

IANA maintains the official registry. When a port in this range is assigned, it's documented, usually tied to an RFC or formal specification. When it's unassigned, it simply doesn't appear in the registry.

Port 890 is one of thousands of unassigned well-known ports. But unlike most unassigned ports, this one has a story.

The NetInfo Ghost

NetInfo was Apple's hierarchical distributed database system, used in NeXTSTEP, OpenStep, and early Mac OS X to store administrative data—user accounts, group configurations, network filesystems, printer settings.³

It ran on RPC (Remote Procedure Call) infrastructure and used ports in the 600-1023 range. Various port databases list port 890 specifically for NetInfo services, though the connection between this exact port number and NetInfo is unclear from available documentation.

NetInfo was completely removed from Mac OS X with version 10.5 Leopard in October 2007.³ It was replaced by Open Directory. The service has been dead for nearly two decades.

But port databases don't forget. The entry persists. You can still find references claiming port 890 is "used by NetInfo" in present tense, describing a service that stopped existing when George W. Bush was president.

This is how the Internet accumulates archaeological layers.

What Actually Listens Here

On a modern system, port 890 is usually silent. No service binds to it by default. If something is listening on port 890 on your network, it's either:

• Custom software that happened to choose this port number
• Legacy Apple systems (pre-2007) still running ancient OS versions
• Malware using an unusual port to avoid detection
• Testing or development services

You can check what's listening with:

# On macOS/Linux
sudo lsof -i :890

# On Windows
netstat -ano | findstr :890

If nothing returns, the port is closed. If something appears, investigate what process owns it.

Why Unassigned Ports Matter

The existence of thousands of unassigned well-known ports might seem wasteful. Why reserve 1,024 ports when only a few hundred are actually assigned?

Because the Internet was designed for a future its creators couldn't predict. Leaving ports unassigned means new fundamental services can be added without conflict. It means port 890 could still be officially assigned to something tomorrow.

The well-known range is finite but not full. That space is deliberate. It's room to grow.

The Memory of Networks

Port databases like SpeedGuide.net and others serve a useful purpose—they document what's actually observed on networks, not just what's officially assigned. They capture the gap between specification and reality.

But they also preserve obsolescence. NetInfo entries persist because removing them requires someone to actively decide "this is dead enough to delete." That threshold is fuzzy. How long does a service need to be gone before it's truly gone?

Port 890 exists in that liminal space. Officially unassigned. Practically obsolete. Documented as active. A ghost in the registry.

This is what networks remember. Not just what's alive, but what used to be.