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// Other services

Port 1742: 3Com-nsd

Port 1742 is assigned by IANA to 3Com-nsd (3Com-nsd).

1742

How 3Com-nsd works

Other services
client:17423Com-nsdresponse client:17423Com-nsdresponse

The client sends a request to port 1742 and the 3Com-nsd 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 1742 dangerous?

We have no specific security note for port 1742. 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 1742

ServicePortTransportDescriptionReferenceUpdated
3Com-nsd 1742 TCP, UDP 3Com-nsd - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 1742, and is it reachable?

Linux

sudo ss -ltnup 'sport = :1742'      # process listening on 1742
sudo lsof -nP -i :1742

macOS

sudo lsof -nP -i :1742

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 1742 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 1742
netstat -ano | findstr :1742

From another machine

nmap -p 1742 -sV <host>
sudo nmap -sU -p 1742 <host>
nc -zv <host> 1742

Block it in the firewall

sudo ufw deny 1742/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 1742" -Direction Inbound -LocalPort 1742 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 1742 used for?

Port 1742 is assigned by IANA to 3Com-nsd (3Com-nsd).

Is port 1742 TCP or UDP?

Port 1742 is registered for TCP and UDP.

Is it safe to open port 1742?

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 1742 is open?

On Linux run "ss -ltnup 'sport = :1742'", on macOS "lsof -nP -i :1742", and on Windows "netstat -ano | findstr :1742" to see the local process. From another machine, "nmap -p 1742 <host>" shows whether it is reachable.

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