whatportis.com

Port 5122 services

2 entries are registered on port 512. 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

services registered on this number

transport
tcp · udp

2 transports in use

in transit
0/2

entries encrypted on the wire

worst risk
4/10

2 of 2 iana-registered

Services on this port

ranked by lookups
portservicerisk
:512Rexeccaution
:512comsat & biffcaution

01Rexectcp · iana-registered · risk 4/10

Rexec (Remote Execution Daemon) is a service traditionally used on UNIX systems allowing users to execute commands on a remote machine over a network. It facilitates remote process execution by authenticating with a username and password sent in plain text, which poses significant security risks. While once commonly adopted in trusted internal environments for remote management, Rexec has largely been superseded by more secure technologies due to its inherent vulnerabilities.

port 512 as Rexec →

02comsat & biffudp · iana-registered · risk 4/10

The Comsat service, working alongside the biff notification utility, provides users with real-time notifications of new email arrivals on UNIX systems. It leverages UDP to listen for incoming mail notifications and alerts logged-in users when new messages are received, historically enabling immediate awareness of incoming communications.

port 512 as comsat & biff →
filed underRemote AccessNetwork ServicesSystemEmail

Which one is on your host

ask the machine, not the registry

The registry says what 512 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 ':512\b'
macos
lsof -nP -iTCP:512 -sTCP:LISTEN
windows
netstat -ano | findstr :512

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 512 — 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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