Port 917 — The Ghost in the RPC Range

Port 917 exists in an interesting gap in the Internet's port registry. It's part of the well-known ports range (0-1023)—the space reserved for fundamental Internet services—but IANA has never officially assigned it to anything.¹

The RPC Ghost Town

In the early 2000s, Mac OS X claimed a large swath of well-known ports (600-1023) for RPC-based services, including NetInfo—the hierarchical distributed database that stored administrative data like user accounts, email configurations, and network resources.²

Port 917 sat somewhere in this claimed territory. But whether any actual RPC service ever bound to this specific port is unclear. Apple's documentation mentions the range but doesn't enumerate which ports mapped to which services.

What This Port Actually Is

Status: Unassigned by IANA
Range: Well-known ports (0-1023)
Protocol: Both TCP and UDP
Reality: Probably nothing is listening here on your system

Port 917 is one of hundreds of well-known ports that exist on paper but have no practical use in 2026. The Internet needed 1,024 reserved ports in the early days, but many were defined for services that never gained adoption or died decades ago.

Why Unassigned Ports Matter

The existence of unassigned well-known ports reveals something about the Internet's history. In 1994, IANA allocated the entire 0-1023 range as "well-known," expecting hundreds of new protocols to emerge. Some did. Most didn't.

These empty ports serve a purpose: they're available for future critical services that might need low-numbered ports for legacy compatibility. They're also a reminder that not every space in the Internet's address system needs to be filled.

Checking What's Listening

If you're curious whether anything is actually using port 917 on your machine:

On macOS/Linux:

sudo lsof -i :917
# or
sudo netstat -anp | grep :917

On Windows:

netstat -ano | findstr :917

Most likely, you'll see nothing. That's normal. Port 917 is probably silent on every device in your house.

The NetInfo Legacy

NetInfo itself is long gone—replaced by Open Directory in Mac OS X 10.5 and eventually by more modern directory services. The ports it used, including possibly 917, are relics of a time when distributed databases needed their own dedicated channels in the well-known range.

What remains is the empty space—a port number that exists in the registry but connects to nothing, like a phone number that was never assigned.