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// Other services

Port 539: Apertus Technologies Load Determination

Port 539 is assigned by IANA to apertus-ldp (Apertus Technologies Load Determination).

539

How apertus-ldp works

Other services
client:539apertus-ldpresponse client:539apertus-ldpresponse

The client sends a request to port 539 and the apertus-ldp 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 539 dangerous?

We have no specific security note for port 539. 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 539

ServicePortTransportDescriptionReferenceUpdated
apertus-ldp 539 TCP, UDP Apertus Technologies Load Determination - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 539, and is it reachable?

Linux

sudo ss -ltnup 'sport = :539'      # process listening on 539
sudo lsof -nP -i :539

macOS

sudo lsof -nP -i :539

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 539 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 539
netstat -ano | findstr :539

From another machine

nmap -p 539 -sV <host>
sudo nmap -sU -p 539 <host>
nc -zv <host> 539

Block it in the firewall

sudo ufw deny 539/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 539" -Direction Inbound -LocalPort 539 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 539 used for?

Port 539 is assigned by IANA to apertus-ldp (Apertus Technologies Load Determination).

Is port 539 TCP or UDP?

Port 539 is registered for TCP and UDP.

Is it safe to open port 539?

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 539 is open?

On Linux run "ss -ltnup 'sport = :539'", on macOS "lsof -nP -i :539", and on Windows "netstat -ano | findstr :539" to see the local process. From another machine, "nmap -p 539 <host>" shows whether it is reachable.

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