01Remote Login (rlogin)tcp · iana-registered · risk 4/10
rlogin (Remote Login) provides remote command-line access to Unix systems, allowing users to log in over the network as if they were directly connected.
port 513 as Remote Login (rlogin) →Port 5132 services
2 entries are registered on port 513. 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.
- entries
- 2
- transport
- tcp · udp
- in transit
- 0/2
- worst risk
- 4/10
services registered on this number
2 transports in use
entries encrypted on the wire
2 of 2 iana-registered
Services on this port
| port | service | risk | |||
|---|---|---|---|---|---|
| :513 | Remote Login (rlogin) | TCP | Remote Access | caution | 10.8k |
| :513 | Who Service | UDP | Security | caution | 8.1k |
02Who Serviceudp · iana-registered · risk 4/10
The WHO service on UDP port 513 is a legacy Unix command networking service designed to remotely return information about users logged into a host system. Often bundled with early UNIX systems, it provides details such as usernames, terminal locations, and login times. Due to its age and security concerns, its usage has largely declined with modern alternatives offering enhanced security.
port 513 as Who Service →Which one is on your host
The registry says what 513 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.
- linux
ss -ltnp | grep ':513\b'- macos
lsof -nP -iTCP:513 -sTCP:LISTEN- windows
netstat -ano | findstr :513
On 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 513 — what you actually met is decided by the host, not the registry. If a service is missing here, it belongs in the registry.
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