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// Other services

Port 742: Network based Rev. Cont. Sys.

Port 742 is assigned by IANA to netrcs (Network based Rev. Cont. Sys.).

742

How netrcs works

Other services
client:742netrcsresponse client:742netrcsresponse

The client sends a request to port 742 and the netrcs 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
Well-known (0-1023)
Category
Other services
01 Security

Is port 742 dangerous?

We have no specific security note for port 742. 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 742

ServicePortTransportDescriptionReferenceUpdated
netrcs 742 TCP, UDP Network based Rev. Cont. Sys. - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 742, and is it reachable?

Linux

sudo ss -ltnup 'sport = :742'      # process listening on 742
sudo lsof -nP -i :742

macOS

sudo lsof -nP -i :742

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 742 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 742
netstat -ano | findstr :742

From another machine

nmap -p 742 -sV <host>
sudo nmap -sU -p 742 <host>
nc -zv <host> 742

Block it in the firewall

sudo ufw deny 742/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 742" -Direction Inbound -LocalPort 742 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 742 used for?

Port 742 is assigned by IANA to netrcs (Network based Rev. Cont. Sys.).

Is port 742 TCP or UDP?

Port 742 is registered for TCP and UDP.

Is it safe to open port 742?

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 742 is open?

On Linux run "ss -ltnup 'sport = :742'", on macOS "lsof -nP -i :742", and on Windows "netstat -ano | findstr :742" to see the local process. From another machine, "nmap -p 742 <host>" shows whether it is reachable.

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