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// Other services

Port 3781: ABCvoice server port

Port 3781 is assigned by IANA to abcvoice-port (ABCvoice server port).

3781

How abcvoice-port works

Other services
client:3781abcvoice-portresponse client:3781abcvoice-portresponse

The client sends a request to port 3781 and the abcvoice-port 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 3781 dangerous?

We have no specific security note for port 3781. 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 3781

ServicePortTransportDescriptionReferenceUpdated
abcvoice-port 3781 TCP, UDP ABCvoice server port - 2003-06

// source: IANA service name and port number registry

03 Check it

Which program uses port 3781, and is it reachable?

Linux

sudo ss -ltnup 'sport = :3781'      # process listening on 3781
sudo lsof -nP -i :3781

macOS

sudo lsof -nP -i :3781

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 3781 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 3781
netstat -ano | findstr :3781

From another machine

nmap -p 3781 -sV <host>
sudo nmap -sU -p 3781 <host>
nc -zv <host> 3781

Block it in the firewall

sudo ufw deny 3781/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 3781" -Direction Inbound -LocalPort 3781 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 3781 used for?

Port 3781 is assigned by IANA to abcvoice-port (ABCvoice server port).

Is port 3781 TCP or UDP?

Port 3781 is registered for TCP and UDP.

Is it safe to open port 3781?

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 3781 is open?

On Linux run "ss -ltnup 'sport = :3781'", on macOS "lsof -nP -i :3781", and on Windows "netstat -ano | findstr :3781" to see the local process. From another machine, "nmap -p 3781 <host>" shows whether it is reachable.

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