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// Other services

Port 9966: OKI Data Network Setting Protocol

Port 9966 is assigned by IANA to odnsp (OKI Data Network Setting Protocol).

9966

How odnsp works

Other services
client:9966odnspresponse client:9966odnspresponse

The client sends a request to port 9966 and the odnsp 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 9966 dangerous?

We have no specific security note for port 9966. 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 9966

ServicePortTransportDescriptionReferenceUpdated
odnsp 9966 TCP, UDP OKI Data Network Setting Protocol - 2006-05

// source: IANA service name and port number registry

03 Check it

Which program uses port 9966, and is it reachable?

Linux

sudo ss -ltnup 'sport = :9966'      # process listening on 9966
sudo lsof -nP -i :9966

macOS

sudo lsof -nP -i :9966

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 9966 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 9966
netstat -ano | findstr :9966

From another machine

nmap -p 9966 -sV <host>
sudo nmap -sU -p 9966 <host>
nc -zv <host> 9966

Block it in the firewall

sudo ufw deny 9966/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 9966" -Direction Inbound -LocalPort 9966 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 9966 used for?

Port 9966 is assigned by IANA to odnsp (OKI Data Network Setting Protocol).

Is port 9966 TCP or UDP?

Port 9966 is registered for TCP and UDP.

Is it safe to open port 9966?

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 9966 is open?

On Linux run "ss -ltnup 'sport = :9966'", on macOS "lsof -nP -i :9966", and on Windows "netstat -ano | findstr :9966" to see the local process. From another machine, "nmap -p 9966 <host>" shows whether it is reachable.

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