Port 245 sits in the well-known ports range (0-1023), officially assigned to a service called "LINK" for both TCP and UDP. But here's the thing: no one knows what LINK was supposed to do.
What We Know
Port 245 appears in RFC 1700 (Assigned Numbers, 1994) and earlier registries, simply listed as "link 245/tcp" and "link 245/udp" with the description "LINK."1 The assignment persists in the current IANA registry.2 That's it. No protocol specification. No reference implementation. No documentation explaining its purpose.
The word "link" appears in MILNET documentation referring to message routing fields, but there's no clear connection to port 245's LINK service.3 This is a classic case of an early port reservation that either never got implemented or was implemented so briefly that all traces vanished.
The Well-Known Range
Port 245 falls in the System Ports range (0-1023), the territory assigned by IANA through formal procedures. These numbers were handed out in the Internet's early days when port numbers seemed infinite and optimism ran high. Not every reservation became reality.
What Actually Uses It
In practice? Almost nothing. Port 245 is effectively dormant. Some security sources note that UDP port 245 has been associated with malware in the past,4 but this is opportunistic—malware sometimes uses obscure assigned ports precisely because they're unlikely to be monitored.
If you find port 245 active on your system, it's worth investigating. Legitimate use of this port is extremely rare.
Checking Port 245
To see if anything is listening on port 245:
Linux/macOS:
Windows:
If something appears, research the process carefully. Legitimate software has no reason to use this port.
Why Ghost Ports Matter
Port 245 represents something important about Internet infrastructure: not every plan succeeds. The registry is full of these fossils—ports assigned to services that never shipped, protocols that never got written, ideas that never caught on.
These unused assignments aren't just clutter. They're a historical record of intentions, of what people thought they'd need. Someone requested port 245 for LINK because they believed it would matter. Maybe they ran out of funding. Maybe the protocol got absorbed into something else. Maybe the problem it solved disappeared.
The port remains assigned because removing it serves no purpose. Port numbers aren't scarce in the well-known range—we have 1,024 of them and we've barely filled half. So LINK stays in the registry, a monument to forgotten work.
The Honest Truth
Port 245 doesn't carry anything. It's a number in a list, waiting for a service that will never come. But it still belongs to LINK, because on the Internet, even the ghosts get to keep their address.
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