Port 959 is officially unassigned by the Internet Assigned Numbers Authority (IANA). It sits in a range of 35 consecutive unassigned ports (954-988) within the well-known ports space.1
What Well-Known Ports Are
Ports 0-1023 are called well-known ports or system ports. These were historically assigned by IANA to specific Internet services—port 80 for HTTP, port 443 for HTTPS, port 25 for SMTP. The well-known designation meant "this port has a standard meaning everywhere on the Internet."
But the well-known range wasn't filled sequentially. There are gaps. Port 959 sits in one of the largest gaps, between port 953 (DNS over TLS) and port 989 (FTPS data transfer).
Why Unassigned Ports Exist
Not every conceivable service needed a well-known port. By the time the Internet matured, dynamic port allocation became more common. Services could request a port from the operating system rather than requiring a permanent assignment. The gaps in the well-known range represent services that were never proposed, never standardized, or simply never needed a fixed number.
Port 959 has been waiting since the beginning of the Internet for a service that never arrived.
Informal Uses
Unassigned doesn't mean unused. Services sometimes borrow unassigned ports for local or proprietary purposes.
Port 959 was used by NetInfo on older Mac OS X systems.2 NetInfo was Apple's directory service in Mac OS X versions through Tiger (10.4), handling user accounts, groups, and network configuration data. NetInfo has been replaced by Open Directory and other modern directory services, so this usage is now obsolete.
Because port 959 has no official assignment, there's no guarantee what you'll find listening on it. It could be NetInfo on an old Mac. It could be a custom application. It could be nothing at all.
Checking What's Listening
To see if anything is listening on port 959 on your system:
On Linux or macOS:
On any system with netstat:
On Windows:
If nothing returns, the port is not in use. If something is listening, you'll see the process ID and can investigate further.
Why Unassigned Ports Matter
The well-known ports range is a finite resource. Only 1,024 numbers exist in this space, and once assigned, they're effectively permanent. Unassigned ports like 959 represent flexibility—room for future protocols, space for temporary testing, gaps that prevent the namespace from becoming completely rigid.
They're also a reminder that the Internet's infrastructure wasn't perfectly planned from the start. It grew organically. Some ports got assigned because someone wrote an RFC in 1985. Some ports stayed empty because no one ever needed them.
Port 959 is one of the empty ones. And that's fine. Not every number needs a purpose.
Related Ports
- Port 953 — DNS over TLS (the last assigned port before this gap)
- Port 989 — FTPS data transfer (the first assigned port after this gap)
- Port 990 — FTPS control connection
Frequently Asked Questions
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