CyberHunter
Local dataset, no network
// Other services

Port 3747: LXPRO.COM LinkTest SSL

Port 3747 is assigned by IANA to linktest-s (LXPRO.COM LinkTest SSL).

3747

How linktest-s works

Other services
client:3747linktest-sresponse client:3747linktest-sresponse

The client sends a request to port 3747 and the linktest-s 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 3747 dangerous?

We have no specific security note for port 3747. 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 3747

ServicePortTransportDescriptionReferenceUpdated
linktest-s 3747 TCP, UDP LXPRO.COM LinkTest SSL - 2003-04

// source: IANA service name and port number registry

03 Check it

Which program uses port 3747, and is it reachable?

Linux

sudo ss -ltnup 'sport = :3747'      # process listening on 3747
sudo lsof -nP -i :3747

macOS

sudo lsof -nP -i :3747

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 3747 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 3747
netstat -ano | findstr :3747

From another machine

nmap -p 3747 -sV <host>
sudo nmap -sU -p 3747 <host>
nc -zv <host> 3747

Block it in the firewall

sudo ufw deny 3747/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 3747" -Direction Inbound -LocalPort 3747 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 3747 used for?

Port 3747 is assigned by IANA to linktest-s (LXPRO.COM LinkTest SSL).

Is port 3747 TCP or UDP?

Port 3747 is registered for TCP and UDP.

Is it safe to open port 3747?

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 3747 is open?

On Linux run "ss -ltnup 'sport = :3747'", on macOS "lsof -nP -i :3747", and on Windows "netstat -ano | findstr :3747" to see the local process. From another machine, "nmap -p 3747 <host>" shows whether it is reachable.

05 Related
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