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// IoT & industrial (ICS)

Port 34966: PROFINET secure real-time data transfer over UDP (unicast and multicast)

Port 34966 is assigned by IANA to profinet-rt-sec (PROFINET secure real-time data transfer over UDP (unicast and multicast)).

34966

How profinet-rt-sec works

IoT & industrial (ICS)
controllerPLCprofinet-rt-secno authentication controllerPLCprofinet-rt-secno authentication

A controller sends commands to an industrial device on port 34966, which acts on the physical process.

Transport
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
IoT & industrial (ICS)
01 Security

Is port 34966 dangerous?

We have no specific security note for port 34966. Its risk depends on the program actually listening on it. General advice for iot & industrial (ics) services:

  • Industrial and IoT protocols often have no authentication: never expose them to the Internet.
  • Segment OT networks from IT and use protocol-aware firewalls.
  • Monitor with an ICS-aware intrusion detection system.
02 Registry

IANA registry entries for port 34966

ServicePortTransportDescriptionReferenceUpdated
profinet-rt-sec 34966 UDP PROFINET secure real-time data transfer over UDP (unicast and multicast) - 2026-03-10
-34966-Reserved--

// source: IANA service name and port number registry

03 Check it

Which program uses port 34966, and is it reachable?

Linux

sudo ss -ltnup 'sport = :34966'      # process listening on 34966
sudo lsof -nP -i :34966

macOS

sudo lsof -nP -i :34966

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 34966 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 34966
netstat -ano | findstr :34966

From another machine

nmap -p 34966 -sV <host>
sudo nmap -sU -p 34966 <host>
nc -zv <host> 34966

Block it in the firewall

sudo ufw deny 34966/udp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 34966" -Direction Inbound -LocalPort 34966 -Protocol UDP -Action Block  # Windows
04 FAQ
What is port 34966 used for?

Port 34966 is assigned by IANA to profinet-rt-sec (PROFINET secure real-time data transfer over UDP (unicast and multicast)).

Is port 34966 TCP or UDP?

Port 34966 is registered for UDP.

Is it safe to open port 34966?

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. Industrial and IoT protocols often have no authentication: never expose them to the Internet.

How do I check if port 34966 is open?

On Linux run "ss -ltnup 'sport = :34966'", on macOS "lsof -nP -i :34966", and on Windows "netstat -ano | findstr :34966" to see the local process. From another machine, "nmap -p 34966 <host>" shows whether it is reachable.

05 Related
:1883 MQTT tcp · udp · high risk :8883 MQTT over TLS tcp · udp · moderate risk :502 Modbus TCP tcp · udp · critical risk :102 Siemens S7 (ISO-TSAP) tcp · udp · critical risk :47808 BACnet udp · tcp · critical risk :20000 DNP3 tcp · udp · sctp · critical risk :44818 EtherNet/IP tcp · udp · critical risk :802 Modbus Application Protocol Secure tcp · udp

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