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// Other services

Port 27: NSW User System FE

Port 27 is assigned by IANA to nsw-fe (NSW User System FE).

27

How nsw-fe works

Other services
client:27nsw-feresponse client:27nsw-feresponse

The client sends a request to port 27 and the nsw-fe 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 27 dangerous?

We have no specific security note for port 27. 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 27

ServicePortTransportDescriptionReferenceUpdated
nsw-fe 27 TCP, UDP NSW User System FE - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 27, and is it reachable?

Linux

sudo ss -ltnup 'sport = :27'      # process listening on 27
sudo lsof -nP -i :27

macOS

sudo lsof -nP -i :27

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 27 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 27
netstat -ano | findstr :27

From another machine

nmap -p 27 -sV <host>
sudo nmap -sU -p 27 <host>
nc -zv <host> 27

Block it in the firewall

sudo ufw deny 27/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 27" -Direction Inbound -LocalPort 27 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 27 used for?

Port 27 is assigned by IANA to nsw-fe (NSW User System FE).

Is port 27 TCP or UDP?

Port 27 is registered for TCP and UDP.

Is it safe to open port 27?

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 27 is open?

On Linux run "ss -ltnup 'sport = :27'", on macOS "lsof -nP -i :27", and on Windows "netstat -ano | findstr :27" to see the local process. From another machine, "nmap -p 27 <host>" shows whether it is reachable.

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