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// Other services

Port 3874: SixXS Configuration

Port 3874 is assigned by IANA to sixxsconfig (SixXS Configuration).

3874

How sixxsconfig works

Other services
client:3874sixxsconfigresponse client:3874sixxsconfigresponse

The client sends a request to port 3874 and the sixxsconfig 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 3874 dangerous?

We have no specific security note for port 3874. 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 3874

ServicePortTransportDescriptionReferenceUpdated
sixxsconfig 3874 TCP, UDP SixXS Configuration - 2003-11

// source: IANA service name and port number registry

03 Check it

Which program uses port 3874, and is it reachable?

Linux

sudo ss -ltnup 'sport = :3874'      # process listening on 3874
sudo lsof -nP -i :3874

macOS

sudo lsof -nP -i :3874

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 3874 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 3874
netstat -ano | findstr :3874

From another machine

nmap -p 3874 -sV <host>
sudo nmap -sU -p 3874 <host>
nc -zv <host> 3874

Block it in the firewall

sudo ufw deny 3874/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 3874" -Direction Inbound -LocalPort 3874 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 3874 used for?

Port 3874 is assigned by IANA to sixxsconfig (SixXS Configuration).

Is port 3874 TCP or UDP?

Port 3874 is registered for TCP and UDP.

Is it safe to open port 3874?

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 3874 is open?

On Linux run "ss -ltnup 'sport = :3874'", on macOS "lsof -nP -i :3874", and on Windows "netstat -ano | findstr :3874" to see the local process. From another machine, "nmap -p 3874 <host>" shows whether it is reachable.

05 Related
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