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// Other services

Port 12109: RETS over SSL

Port 12109 is assigned by IANA to rets-ssl (RETS over SSL).

12109

How rets-ssl works

Other services
client:12109#%&@!x9response? client:12109#%&@!x9response?

The client sends a request to port 12109 and the rets-ssl service answers. Everything is encrypted: someone on the path only sees unreadable bytes.

Transport
TCP · UDP
Exposure risk
not rated depends on the program listening
Encryption
EncryptedTLS or built-in crypto
IANA status
Assigned1 registered service
Range
Registered (1024-49151)
Category
Other services
01 Security

Is port 12109 dangerous?

We have no specific security note for port 12109. 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 12109

ServicePortTransportDescriptionReferenceUpdated
rets-ssl 12109 TCP, UDP RETS over SSL - 2003-02

// source: IANA service name and port number registry

03 Check it

Which program uses port 12109, and is it reachable?

Linux

sudo ss -ltnup 'sport = :12109'      # process listening on 12109
sudo lsof -nP -i :12109

macOS

sudo lsof -nP -i :12109

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 12109 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 12109
netstat -ano | findstr :12109

From another machine

nmap -p 12109 -sV <host>
sudo nmap -sU -p 12109 <host>
nc -zv <host> 12109

Block it in the firewall

sudo ufw deny 12109/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 12109" -Direction Inbound -LocalPort 12109 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 12109 used for?

Port 12109 is assigned by IANA to rets-ssl (RETS over SSL).

Is port 12109 TCP or UDP?

Port 12109 is registered for TCP and UDP.

Is it safe to open port 12109?

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 12109 is open?

On Linux run "ss -ltnup 'sport = :12109'", on macOS "lsof -nP -i :12109", and on Windows "netstat -ano | findstr :12109" to see the local process. From another machine, "nmap -p 12109 <host>" shows whether it is reachable.

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