Port 942 is officially unassigned. It exists in the well-known ports range—the prestigious addresses between 0 and 1023—but IANA has never designated an official service for it.
The Well-Known Range
Ports 0 through 1023 are called "well-known ports" or "system ports." These numbers are managed by the Internet Assigned Numbers Authority (IANA) and typically require elevated privileges to bind to on Unix-like systems.1
Getting a well-known port assigned requires going through IETF review. Most were claimed decades ago for foundational Internet services—HTTP on 80, SSH on 22, DNS on 53. But scattered throughout the range are unassigned numbers like 942.
Historical Use: Apple's NetInfo
While never officially registered with IANA, port 942 appears in older documentation as part of Apple's RPC-based service infrastructure. It was associated with NetInfo, Apple's network directory service used in Mac OS X.2
NetInfo was removed entirely from macOS with version 10.5 (Leopard), replaced by Open Directory. The ports it used—including 942—became unused remnants of a deprecated system.
Why Unassigned Ports Matter
Unassigned ports aren't useless. They're available space. They represent flexibility in a system that was designed when no one knew what the Internet would become.
Some remain unassigned because no one has needed them yet. Others were used informally by specific vendors (like Apple) but never formalized through IANA. A few are simply gaps—numbers that fell through the cracks as services claimed their neighbors.
Checking What's Listening
Even though port 942 has no official assignment, something could still be using it on your system. To check what's listening:
On Linux or macOS:
On Windows:
If you find something listening on 942, it's either legacy software from the NetInfo era, a custom application that chose an unassigned port, or potentially something unauthorized that deserves investigation.
The Empty Spaces
The well-known range is full of these ghosts. Ports reserved by position but never claimed. Numbers that had meaning once—or were set aside for meaning that never came.
Port 942 sits there still, waiting. The Internet doesn't forget its addresses, even the ones nobody uses.
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