Port 817 is officially unassigned by IANA. It sits in the well-known port range (0-1023), reserved for system services and protocols, but nobody ever claimed it for an official standard.
What Range This Belongs To
Ports 0-1023 are called well-known ports. They're reserved for system services and require root/administrator privileges to bind to on most operating systems. IANA manages this range strictly—every assignment requires documentation and justification.
Port 817 is one of the gaps. Not every number between 0 and 1023 has an assigned service. Some remain unassigned, waiting for a protocol important enough to claim them.
The Ghost of NetInfo
While port 817 has no official assignment, it has a history. Older Mac OS X systems (before 10.5) used ports in the 600-1023 range for RPC-based services, including NetInfo—a distributed database that managed user accounts, printer configurations, and other administrative data.1
NetInfo is gone now. Mac OS X 10.5 Leopard (released in 2007) replaced it entirely with Open Directory. The RPC services that once listened on ports like 817 disappeared with it.2
Port 817 outlived its purpose. It was used by services that no longer exist, and it was never officially documented in the IANA registry.
Why Unassigned Ports Matter
The gaps in the port numbering system aren't accidents—they're breathing room.
When a new protocol needs a port, IANA has space to assign one. When organizations need ports for internal services, they can temporarily use unassigned numbers without colliding with official standards (though the registered port range 1024-49151 is better suited for this).
Unassigned ports also tell you something: if you find traffic on port 817, it's not a standard protocol. It's either:
- Legacy software (like old Mac OS X RPC services)
- Custom internal applications
- Malware trying to hide in unused space
How to Check What's Listening
On Linux or macOS:
On Windows:
If something is listening on port 817, it's worth investigating. It's not supposed to be there.
The Takeaway
Port 817 is a number without a protocol. It belongs to the well-known range but has no well-known purpose. It was briefly inhabited by Mac OS X services that are now obsolete, and it remains officially unassigned.
The Internet has 65,535 ports. Not all of them need to be used. Some exist just to remind us that the numbering system has room to grow.
Frequently Asked Questions About Port 817
Ήταν χρήσιμη αυτή η σελίδα;