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// Other services

Port 3681: BTS X73 Port

Port 3681 is assigned by IANA to bts-x73 (BTS X73 Port).

3681

How bts-x73 works

Other services
client:3681bts-x73response client:3681bts-x73response

The client sends a request to port 3681 and the bts-x73 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 3681 dangerous?

We have no specific security note for port 3681. 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 3681

ServicePortTransportDescriptionReferenceUpdated
bts-x73 3681 TCP, UDP BTS X73 Port - 2003-01

// source: IANA service name and port number registry

03 Check it

Which program uses port 3681, and is it reachable?

Linux

sudo ss -ltnup 'sport = :3681'      # process listening on 3681
sudo lsof -nP -i :3681

macOS

sudo lsof -nP -i :3681

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 3681 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 3681
netstat -ano | findstr :3681

From another machine

nmap -p 3681 -sV <host>
sudo nmap -sU -p 3681 <host>
nc -zv <host> 3681

Block it in the firewall

sudo ufw deny 3681/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 3681" -Direction Inbound -LocalPort 3681 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 3681 used for?

Port 3681 is assigned by IANA to bts-x73 (BTS X73 Port).

Is port 3681 TCP or UDP?

Port 3681 is registered for TCP and UDP.

Is it safe to open port 3681?

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 3681 is open?

On Linux run "ss -ltnup 'sport = :3681'", on macOS "lsof -nP -i :3681", and on Windows "netstat -ano | findstr :3681" to see the local process. From another machine, "nmap -p 3681 <host>" shows whether it is reachable.

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