The Port That Lost Its Assignment
Port 658 sits in the well-known port range (0-1023), the space reserved for fundamental Internet services. These ports are controlled by IANA—the Internet Assigned Numbers Authority—and assignments here are supposed to be permanent.
But port 658 is different. It used to have an official assignment. And then it didn't.
What TenFold Was
Port 658 was assigned to TenFold, a Mac OS X RPC-based service used by NetInfo.1 NetInfo was Apple's directory service system in classic Mac OS X, handling user accounts, network configuration, and other system information. The service ran on port 658/UDP, sitting among the range of RPC ports (600-1023) that Mac OS X reserved for internal communication.
If you ran a Mac between the late 1990s and mid-2000s, NetInfo was quietly running in the background, and port 658 was part of that infrastructure.
The Removal
On May 18, 2017, IANA removed the port 658 assignment from the official registry.2 The TenFold entry was deleted. No replacement was assigned.
Why? Because NetInfo was already dead. Apple deprecated NetInfo in Mac OS X 10.5 Leopard (2007) and replaced it with Open Directory. By 2017, NetInfo had been gone for a decade. The port assignment was just catching up with reality.
Port 658 now appears in the IANA registry as unassigned—a gap in the numbering where a service used to be.
What This Means
Port 658 is technically available for reassignment, but IANA rarely reuses well-known ports, especially ones below 1024. The security implications are too messy—old systems might still reference the port, firewalls might have rules mentioning it, and reusing a number creates confusion.
So port 658 just sits there. Empty. A reminder that even infrastructure protocols can become obsolete.
If you see traffic on port 658 today, it's probably one of two things:
- A very old Mac still running a NetInfo-based system (unlikely but possible)
- An unofficial service using the port because it's technically unassigned
Checking What's Using Port 658
On Linux or macOS:
On Windows:
If something is listening on port 658, you'll need to identify what process owns it. The port has no official meaning anymore—whatever's there is either legacy or custom.
Why Unassigned Ports Matter
The existence of ports like 658 reveals something important: the Internet's infrastructure is not static. Services get created, standardized, deployed widely—and then abandoned. Protocols die. Software evolves. And sometimes the port numbers get left behind.
The well-known port range is supposed to be the stable foundation of Internet communication. But even foundations crack. Port 658 is proof.
The Internet moves on. The port numbers remember.
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