TCP and UDP use 16-bit port numbers, so the complete numeric range is 0 through 65535. Port zero is reserved, 1–1023 is the system or well-known range, 1024–49151 is the user or registered range, and 49152–65535 is dynamic or private. This lookup reports that classification and a small set of common service conventions.
A port number is not proof of a protocol. Port 443 conventionally carries HTTPS, but software can listen on any available port and a firewall can block it. tryb never opens a socket or scans a host; it only explains what the pasted number commonly means.
Three-digit values from 100 through 599 are also valid HTTP status syntax. The dedicated status-code interpretation ranks higher for those values, while the port interpretation remains available at lower confidence. Values such as 8080 or 5432 are much stronger port candidates.
Edge cases worth knowing
- Port zero
- Zero is in the 16-bit field but is reserved and is not a valid destination service port. APIs may use zero as a request to allocate an ephemeral local port.
- A value such as 404
- 404 is both a valid port number and a standardized HTTP status. tryb leads with the status interpretation and keeps port as a secondary possibility.
- Dynamic ports
- A number in 49152–65535 is often selected temporarily by an operating system, but it can still be bound explicitly. Range describes convention, not current use.
Common mistakes
- Assuming a familiar port number proves which application protocol is running.
- Treating a registered service name as proof that a remote port is open.
- Accepting values above 65535 even though the transport header has only 16 bits.
- Calling every port below 1024 insecure; security depends on protocol, configuration, and context.