CyberHunter
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// Other services

Port 171: Network Innovations Multiplex

Port 171 is assigned by IANA to multiplex (Network Innovations Multiplex).

171

How multiplex works

Other services
client:171multiplexresponse client:171multiplexresponse

The client sends a request to port 171 and the multiplex 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 171 dangerous?

We have no specific security note for port 171. 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 171

ServicePortTransportDescriptionReferenceUpdated
multiplex 171 TCP, UDP Network Innovations Multiplex - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 171, and is it reachable?

Linux

sudo ss -ltnup 'sport = :171'      # process listening on 171
sudo lsof -nP -i :171

macOS

sudo lsof -nP -i :171

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 171 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 171
netstat -ano | findstr :171

From another machine

nmap -p 171 -sV <host>
sudo nmap -sU -p 171 <host>
nc -zv <host> 171

Block it in the firewall

sudo ufw deny 171/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 171" -Direction Inbound -LocalPort 171 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 171 used for?

Port 171 is assigned by IANA to multiplex (Network Innovations Multiplex).

Is port 171 TCP or UDP?

Port 171 is registered for TCP and UDP.

Is it safe to open port 171?

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 171 is open?

On Linux run "ss -ltnup 'sport = :171'", on macOS "lsof -nP -i :171", and on Windows "netstat -ano | findstr :171" to see the local process. From another machine, "nmap -p 171 <host>" shows whether it is reachable.

05 Related
:4444 Metasploit default / krb524 tcp · udp · high risk :31337 Back Orifice / elite tcp · udp · high risk :1 TCP Port Service Multiplexer tcp · udp :5 Remote Job Entry tcp · udp :9 Discard tcp · udp · sctp · dccp :11 Active Users tcp · udp :17 Quote of the Day tcp · udp :18 Message Send Protocol (historic) tcp · udp

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