CyberHunter
Local dataset, no network
// Other services

Port 1531: rap-listen

Port 1531 is assigned by IANA to rap-listen (rap-listen).

1531

How rap-listen works

Other services
client:1531rap-listenresponse client:1531rap-listenresponse

The client sends a request to port 1531 and the rap-listen 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
Registered (1024-49151)
Category
Other services
01 Security

Is port 1531 dangerous?

We have no specific security note for port 1531. 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 1531

ServicePortTransportDescriptionReferenceUpdated
rap-listen 1531 TCP, UDP rap-listen - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 1531, and is it reachable?

Linux

sudo ss -ltnup 'sport = :1531'      # process listening on 1531
sudo lsof -nP -i :1531

macOS

sudo lsof -nP -i :1531

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 1531 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 1531
netstat -ano | findstr :1531

From another machine

nmap -p 1531 -sV <host>
sudo nmap -sU -p 1531 <host>
nc -zv <host> 1531

Block it in the firewall

sudo ufw deny 1531/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 1531" -Direction Inbound -LocalPort 1531 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 1531 used for?

Port 1531 is assigned by IANA to rap-listen (rap-listen).

Is port 1531 TCP or UDP?

Port 1531 is registered for TCP and UDP.

Is it safe to open port 1531?

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 1531 is open?

On Linux run "ss -ltnup 'sport = :1531'", on macOS "lsof -nP -i :1531", and on Windows "netstat -ano | findstr :1531" to see the local process. From another machine, "nmap -p 1531 <host>" shows whether it is reachable.

05 Related
:4444 Metasploit default / krb524 tcp · udp · high risk :31337 Back Orifice / elite tcp · udp · high risk :1 TCP Port Service Multiplexer tcp · udp :5 Remote Job Entry tcp · udp :9 Discard tcp · udp · sctp · dccp :11 Active Users tcp · udp :17 Quote of the Day tcp · udp :18 Message Send Protocol (historic) tcp · udp

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