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// Other services

Port 431: UTMPCD

Port 431 is assigned by IANA to utmpcd (UTMPCD).

431

How utmpcd works

Other services
client:431utmpcdresponse client:431utmpcdresponse

The client sends a request to port 431 and the utmpcd service answers.

Transport
TCP · UDP
Exposure risk
not rated depends on the program listening
Encryption
Unknownnot stated by the registry
IANA status
Assigned1 registered service
Range
Well-known (0-1023)
Category
Other services
01 Security

Is port 431 dangerous?

We have no specific security note for port 431. Its risk depends on the program actually listening on it. General advice for other services services:

  • Close the port if nothing on the host needs it.
  • Identify the process that listens on it (commands below) before opening it in a firewall.
  • Expose a service only to the networks that use it.
02 Registry

IANA registry entries for port 431

ServicePortTransportDescriptionReferenceUpdated
utmpcd 431 TCP, UDP UTMPCD - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 431, and is it reachable?

Linux

sudo ss -ltnup 'sport = :431'      # process listening on 431
sudo lsof -nP -i :431

macOS

sudo lsof -nP -i :431

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 431 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 431
netstat -ano | findstr :431

From another machine

nmap -p 431 -sV <host>
sudo nmap -sU -p 431 <host>
nc -zv <host> 431

Block it in the firewall

sudo ufw deny 431/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 431" -Direction Inbound -LocalPort 431 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 431 used for?

Port 431 is assigned by IANA to utmpcd (UTMPCD).

Is port 431 TCP or UDP?

Port 431 is registered for TCP and UDP.

Is it safe to open port 431?

It depends on the program that listens on it. Open it only for a service you know and only to the networks that need it. Close the port if nothing on the host needs it.

How do I check if port 431 is open?

On Linux run "ss -ltnup 'sport = :431'", on macOS "lsof -nP -i :431", and on Windows "netstat -ano | findstr :431" to see the local process. From another machine, "nmap -p 431 <host>" shows whether it is reachable.

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