CyberHunter
Local dataset, no network
// Other services

Port 3971: LANrev Server

Port 3971 is assigned by IANA to lanrevserver (LANrev Server).

3971

How lanrevserver works

Other services
client:3971lanrevserverresponse client:3971lanrevserverresponse

The client sends a request to port 3971 and the lanrevserver 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 3971 dangerous?

We have no specific security note for port 3971. 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 3971

ServicePortTransportDescriptionReferenceUpdated
lanrevserver 3971 TCP, UDP LANrev Server - 2005-08

// source: IANA service name and port number registry

03 Check it

Which program uses port 3971, and is it reachable?

Linux

sudo ss -ltnup 'sport = :3971'      # process listening on 3971
sudo lsof -nP -i :3971

macOS

sudo lsof -nP -i :3971

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 3971 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 3971
netstat -ano | findstr :3971

From another machine

nmap -p 3971 -sV <host>
sudo nmap -sU -p 3971 <host>
nc -zv <host> 3971

Block it in the firewall

sudo ufw deny 3971/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 3971" -Direction Inbound -LocalPort 3971 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 3971 used for?

Port 3971 is assigned by IANA to lanrevserver (LANrev Server).

Is port 3971 TCP or UDP?

Port 3971 is registered for TCP and UDP.

Is it safe to open port 3971?

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 3971 is open?

On Linux run "ss -ltnup 'sport = :3971'", on macOS "lsof -nP -i :3971", and on Windows "netstat -ano | findstr :3971" to see the local process. From another machine, "nmap -p 3971 <host>" shows whether it is reachable.

05 Related
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