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// Other services

Port 4451: CTI System Msg

Port 4451 is assigned by IANA to ctisystemmsg (CTI System Msg).

4451

How ctisystemmsg works

Other services
client:4451ctisystemmsgresponse client:4451ctisystemmsgresponse

The client sends a request to port 4451 and the ctisystemmsg 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 4451 dangerous?

We have no specific security note for port 4451. 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 4451

ServicePortTransportDescriptionReferenceUpdated
ctisystemmsg 4451 TCP, UDP CTI System Msg - 2011-10-28

// source: IANA service name and port number registry

03 Check it

Which program uses port 4451, and is it reachable?

Linux

sudo ss -ltnup 'sport = :4451'      # process listening on 4451
sudo lsof -nP -i :4451

macOS

sudo lsof -nP -i :4451

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 4451 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 4451
netstat -ano | findstr :4451

From another machine

nmap -p 4451 -sV <host>
sudo nmap -sU -p 4451 <host>
nc -zv <host> 4451

Block it in the firewall

sudo ufw deny 4451/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 4451" -Direction Inbound -LocalPort 4451 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 4451 used for?

Port 4451 is assigned by IANA to ctisystemmsg (CTI System Msg).

Is port 4451 TCP or UDP?

Port 4451 is registered for TCP and UDP.

Is it safe to open port 4451?

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 4451 is open?

On Linux run "ss -ltnup 'sport = :4451'", on macOS "lsof -nP -i :4451", and on Windows "netstat -ano | findstr :4451" to see the local process. From another machine, "nmap -p 4451 <host>" shows whether it is reachable.

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