Port 809 is unassigned. No official service uses it. No protocol waits behind it. It's an empty address in the Internet's directory.
What "Unassigned" Means
Port numbers from 0-1023 are called well-known ports. They're managed by the Internet Assigned Numbers Authority (IANA), the organization that decides which services get which numbers.1
Some of these ports have famous occupants:
- Port 80: HTTP
- Port 443: HTTPS
- Port 22: SSH
Others, like port 809, remain empty. They were reserved for future use but never assigned to any service.
Why Unassigned Ports Matter
The well-known ports range has 1,024 possible addresses. Not all of them are filled. The gaps—the unassigned ports—serve a purpose:
They're available for future protocols. If someone designs a new service important enough to warrant a well-known port number, IANA can assign it one of these empty slots.
They prevent collisions. Because port 809 isn't officially assigned, applications generally avoid using it. This prevents two different services from accidentally trying to use the same port.
They can be used unofficially. While there's no official service on port 809, nothing stops a developer from configuring their application to listen here. Custom software, internal tools, or experimental protocols sometimes claim unassigned ports.
Checking What's Actually Using Port 809
Just because port 809 has no official assignment doesn't mean nothing is listening on it on your machine. To check:
On Linux or macOS:
On Windows:
If something appears, it's unofficial—custom software or a service configured to use this port locally.
The Landscape of Empty Ports
Port 809 sits among several other unassigned ports in the 800s range. Just below it, port 808 is sometimes used for HTTP alternate servers. Just above it, port 810 is officially assigned to FCP (File Copy Protocol), though FCP itself is rarely used today.1
The unassigned ports are the quiet streets in a crowded city. They exist, they have addresses, but no one has built anything there yet.
Should You Use Port 809?
For production services that need well-known ports, no. The proper process is to apply to IANA for an official assignment.2
For internal tools, testing, or services that only run on your own network? It's available. Nothing official will conflict with it. Just know that your use is unofficial—another developer or organization might choose the same number for their custom application, and there would be no central authority to resolve the collision.
The unassigned ports are the commons. Use them carefully.
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