2 entries are registered on port 256. It is a well-known port (0–1023) — assignments here are IANA's, and a service found on one is usually the service that was assigned it.
services registered on this number
2 transports in use
entries encrypted on the wire
1 of 2 iana-registered
| port | service | proto | category | risk | views |
|---|---|---|---|---|---|
| :256 | 2DEV 2SP | TCPUDP | Network Services | caution | 7.0k |
| :256 | RAP | TCPUDP | — | safe | 0 |
Port 256 is an unofficial assignment commonly referenced as '2DEV 2SP'. It does not correspond to a widespread standardized service but may be utilized by specialized or proprietary protocols during development or in niche deployments. As such, its behavior can vary depending on the environment, and it does not represent a recognized industry standard service port.
port 256 as 2DEV 2SP →RAP is an obscure service assigned to TCP and UDP port 256, with little evidence of widespread deployment.
port 256 as RAP →The registry says what 256 is registered to. What is listening on it right now is decided by the host, and only the host can be asked. Each of these prints the process behind the socket.
ss -ltnp | grep ':256\b'lsof -nP -iTCP:256 -sTCP:LISTENnetstat -ano | findstr :256On Linux and Windows the process name comes back with the socket; on macOS lsof needs sudo to name a process that isn't yours. Match what it prints against the 2 entries above.
A port number is not a service. Anything may listen on 256 — what you actually met is decided by the host, not the registry. If a service is missing here, it belongs in the registry.
contribute an entry