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// Other services

Port 3456: VAT default data

Port 3456 is assigned by IANA to vat (VAT default data).

3456

How vat works

Other services
client:3456vatresponse client:3456vatresponse

The client sends a request to port 3456 and the vat 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 3456 dangerous?

We have no specific security note for port 3456. 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 3456

ServicePortTransportDescriptionReferenceUpdated
vat 3456 TCP, UDP VAT default data - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 3456, and is it reachable?

Linux

sudo ss -ltnup 'sport = :3456'      # process listening on 3456
sudo lsof -nP -i :3456

macOS

sudo lsof -nP -i :3456

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 3456 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 3456
netstat -ano | findstr :3456

From another machine

nmap -p 3456 -sV <host>
sudo nmap -sU -p 3456 <host>
nc -zv <host> 3456

Block it in the firewall

sudo ufw deny 3456/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 3456" -Direction Inbound -LocalPort 3456 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 3456 used for?

Port 3456 is assigned by IANA to vat (VAT default data).

Is port 3456 TCP or UDP?

Port 3456 is registered for TCP and UDP.

Is it safe to open port 3456?

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 3456 is open?

On Linux run "ss -ltnup 'sport = :3456'", on macOS "lsof -nP -i :3456", and on Windows "netstat -ano | findstr :3456" to see the local process. From another machine, "nmap -p 3456 <host>" shows whether it is reachable.

05 Related
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