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// Other services

Port 3809: Java Desktop System Configuration Agent

Port 3809 is assigned by IANA to apocd (Java Desktop System Configuration Agent).

3809

How apocd works

Other services
client:3809apocdresponse client:3809apocdresponse

The client sends a request to port 3809 and the apocd 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 3809 dangerous?

We have no specific security note for port 3809. 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 3809

ServicePortTransportDescriptionReferenceUpdated
apocd 3809 TCP, UDP Java Desktop System Configuration Agent - 2006-03

// source: IANA service name and port number registry

03 Check it

Which program uses port 3809, and is it reachable?

Linux

sudo ss -ltnup 'sport = :3809'      # process listening on 3809
sudo lsof -nP -i :3809

macOS

sudo lsof -nP -i :3809

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 3809 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 3809
netstat -ano | findstr :3809

From another machine

nmap -p 3809 -sV <host>
sudo nmap -sU -p 3809 <host>
nc -zv <host> 3809

Block it in the firewall

sudo ufw deny 3809/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 3809" -Direction Inbound -LocalPort 3809 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 3809 used for?

Port 3809 is assigned by IANA to apocd (Java Desktop System Configuration Agent).

Is port 3809 TCP or UDP?

Port 3809 is registered for TCP and UDP.

Is it safe to open port 3809?

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 3809 is open?

On Linux run "ss -ltnup 'sport = :3809'", on macOS "lsof -nP -i :3809", and on Windows "netstat -ano | findstr :3809" to see the local process. From another machine, "nmap -p 3809 <host>" shows whether it is reachable.

05 Related
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