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// Other services

Port 3742: CST - Configuration & Service Tracker

Port 3742 is assigned by IANA to cst-port (CST - Configuration & Service Tracker).

3742

How cst-port works

Other services
client:3742cst-portresponse client:3742cst-portresponse

The client sends a request to port 3742 and the cst-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 3742 dangerous?

We have no specific security note for port 3742. 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 3742

ServicePortTransportDescriptionReferenceUpdated
cst-port 3742 TCP, UDP CST - Configuration & Service Tracker - 2003-04

// source: IANA service name and port number registry

03 Check it

Which program uses port 3742, and is it reachable?

Linux

sudo ss -ltnup 'sport = :3742'      # process listening on 3742
sudo lsof -nP -i :3742

macOS

sudo lsof -nP -i :3742

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 3742 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 3742
netstat -ano | findstr :3742

From another machine

nmap -p 3742 -sV <host>
sudo nmap -sU -p 3742 <host>
nc -zv <host> 3742

Block it in the firewall

sudo ufw deny 3742/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 3742" -Direction Inbound -LocalPort 3742 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 3742 used for?

Port 3742 is assigned by IANA to cst-port (CST - Configuration & Service Tracker).

Is port 3742 TCP or UDP?

Port 3742 is registered for TCP and UDP.

Is it safe to open port 3742?

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 3742 is open?

On Linux run "ss -ltnup 'sport = :3742'", on macOS "lsof -nP -i :3742", and on Windows "netstat -ano | findstr :3742" to see the local process. From another machine, "nmap -p 3742 <host>" shows whether it is reachable.

05 Related
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