Port 746 has been registered with the Internet Assigned Numbers Authority (IANA) for decades. It has no assigned service. Both TCP and UDP on port 746 are marked "unassigned" in the official registry.1
This is more common than you might think. The well-known ports range is full of reserved numbers that never got used.
What "Unassigned" Means
Port 746 lives in the well-known ports range (0-1023). These are system ports, typically requiring root or administrator privileges to bind. They're meant for standard Internet services—things like HTTP (80), HTTPS (443), SSH (22).
But not every number got a purpose.
IANA maintains the official registry of port assignments. Port 746 appears in that registry, but the service name field is blank. It's been claimed but never used. Reserved, but for nothing specific.
This doesn't mean port 746 can't be used. Any application can listen on port 746 if it has the necessary permissions. It just means there's no standard protocol or service associated with this number. If you see traffic on port 746, it's not following any official convention—it's something custom, something local, or something that chose an arbitrary port.
Why Unassigned Ports Exist
The well-known ports range was established decades ago when the Internet was smaller and people thought they could plan for everything. IANA reserved blocks of ports for future services, protocols that might need a standard number someday.
Some of those protocols never materialized. Some services died before they needed their own port. Some numbers were reserved "just in case" and that case never came.
Port 746 is one of those numbers. Reserved, registered, but never given a job.
What Might Be Listening on Port 746
If you discover something listening on port 746, it's likely:
- A custom application — Someone needed a port number and picked this one because it was available
- A misconfigured service — Something meant to run on a different port but got set to 746 by mistake
- Malware or unauthorized software — Attackers sometimes use unassigned ports specifically because they're not monitored
To check what's listening on port 746:
On Linux or macOS:
On Windows:
If something is listening and you don't recognize it, investigate. Unassigned ports have no legitimate standard service, so anything using port 746 should be identifiable and intentional.
The Ghost Ports
Port 746 is part of a larger phenomenon. Scattered throughout the well-known range are unassigned numbers—reserved but never claimed, registered but never defined. They're the gaps in the system, the numbers that were set aside for a future that didn't arrive.
The Internet moved on. Services found their ports. Port 746 remained empty.
It's still registered. Still reserved. Still sitting there in the IANA list, waiting for a purpose that may never come.
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