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Port 5312 services

2 entries are registered on port 531. 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

1 of 2 iana-registered

Services on this port

ranked by lookups
portservicerisk
:531AOL IM and IRCcaution
:531Conference chatsafe

01AOL IM and IRCtcp · udp · unofficial · risk 4/10

Port 531 is primarily recognized for its association with legacy instant messaging services like AOL Instant Messenger (AIM) and the Internet Relay Chat (IRC) protocol. It facilitated real-time text communication between users over the internet, supporting both direct peer-to-peer messaging and participation in chat rooms. Being unofficial, the use of this port has diminished over the years; nevertheless, understanding its role helps in managing older systems or potential residual network traffic.

port 531 as AOL IM and IRC →
filed underVoice and Chat

Which one is on your host

ask the machine, not the registry

The registry says what 531 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 ':531\b'
macos
lsof -nP -iTCP:531 -sTCP:LISTEN
windows
netstat -ano | findstr :531

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 531 — 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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