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// Remote access

Port 4089: OpenCORE Remote Control Service

Port 4089 is assigned by IANA to opencore (OpenCORE Remote Control Service).

4089

How opencore works

Remote access
terminal:4089opencore terminal:4089opencore

The client opens a session to port 4089: each command typed is sent to the server, which runs it and returns the output.

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
Remote access
01 Security

Is port 4089 dangerous?

We have no specific security note for port 4089. Its risk depends on the program actually listening on it. General advice for remote access services:

  • Do not expose remote administration directly: use a VPN or a zero-trust access proxy.
  • Require MFA or key-based authentication and lock out brute-force attempts.
  • Log every login and alert on new source addresses.
02 Registry

IANA registry entries for port 4089

ServicePortTransportDescriptionReferenceUpdated
opencore 4089 TCP, UDP OpenCORE Remote Control Service - 2006-07

// source: IANA service name and port number registry

03 Check it

Which program uses port 4089, and is it reachable?

Linux

sudo ss -ltnup 'sport = :4089'      # process listening on 4089
sudo lsof -nP -i :4089

macOS

sudo lsof -nP -i :4089

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 4089 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 4089
netstat -ano | findstr :4089

From another machine

nmap -p 4089 -sV <host>
sudo nmap -sU -p 4089 <host>
nc -zv <host> 4089

Block it in the firewall

sudo ufw deny 4089/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 4089" -Direction Inbound -LocalPort 4089 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 4089 used for?

Port 4089 is assigned by IANA to opencore (OpenCORE Remote Control Service).

Is port 4089 TCP or UDP?

Port 4089 is registered for TCP and UDP.

Is it safe to open port 4089?

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. Do not expose remote administration directly: use a VPN or a zero-trust access proxy.

How do I check if port 4089 is open?

On Linux run "ss -ltnup 'sport = :4089'", on macOS "lsof -nP -i :4089", and on Windows "netstat -ano | findstr :4089" to see the local process. From another machine, "nmap -p 4089 <host>" shows whether it is reachable.

05 Related
:22 SSH tcp · udp · sctp · moderate risk :3389 RDP tcp · udp · critical risk :23 Telnet tcp · udp · critical risk :5900 VNC tcp · udp · critical risk :5985 WinRM (HTTP) tcp · udp · high risk :5986 WinRM (HTTPS) tcp · udp · high risk :10000 Webmin tcp · udp · high risk :89 SU/MIT Telnet Gateway tcp · udp

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