Port 842: Unassigned — A reserved number without a service

Port 842 has no official service assignment. Despite falling within the well-known ports range (0-1023), IANA has never allocated this port number to any protocol or application.

The Unassigned Range

Port 842 sits in a block of thirteen consecutive unassigned ports: 834 through 846.¹ These ports exist in the registry but remain unclaimed—reserved numbers without services attached to them.

In a range where most ports have been spoken for since the early days of the Internet, this gap is notable. Ports immediately around this range have clear purposes: port 830 carries NETCONF over TLS, port 853 carries DNS over TLS. But 834-846 remain empty.

Well-Known But Unused

The well-known ports range (0-1023) is the most restricted portion of the port number space. On Unix-like systems, only processes running with superuser privileges can bind to these ports. They're meant for fundamental Internet services—the protocols everyone depends on.

Port 842 has that privileged status but no assigned purpose. It's reserved but not required.

Unofficial Usage

Some older documentation references port 842 in connection with NetInfo, an administrative database system used in Mac OS X Server before version 10.5.² However, this was never an official IANA assignment. NetInfo was removed from macOS in 2007, replaced entirely by Open Directory.

If port 842 was ever used for NetInfo RPC services, it was informal—a port number chosen for internal use but never registered with IANA.

Checking What's Listening

Even though port 842 is officially unassigned, you can check if anything on your system is using it:

On Linux/macOS:

sudo lsof -i :842
netstat -an | grep :842

On Windows:

netstat -ano | findstr :842

If nothing appears, the port is closed—which is the expected state for an unassigned port.

Why Unassigned Ports Matter

Unassigned ports aren't useless—they're available. Every new protocol needs a port number. When someone designs a service that deserves a place in the well-known range, IANA can assign one of these unclaimed numbers.

The existence of unassigned ports means the Internet still has room to grow. The registry isn't full. New fundamental services can still claim their place.

Port 842 is waiting. Maybe it will remain unassigned forever. Or maybe someday a protocol will need this exact number, and IANA will grant it—and port 842 will finally have a purpose.