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// Other services

Port 173: Xyplex

Port 173 is assigned by IANA to xyplex-mux (Xyplex).

173

How xyplex-mux works

Other services
client:173xyplex-muxresponse client:173xyplex-muxresponse

The client sends a request to port 173 and the xyplex-mux 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 173 dangerous?

We have no specific security note for port 173. 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 173

ServicePortTransportDescriptionReferenceUpdated
xyplex-mux 173 TCP, UDP Xyplex - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 173, and is it reachable?

Linux

sudo ss -ltnup 'sport = :173'      # process listening on 173
sudo lsof -nP -i :173

macOS

sudo lsof -nP -i :173

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 173 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 173
netstat -ano | findstr :173

From another machine

nmap -p 173 -sV <host>
sudo nmap -sU -p 173 <host>
nc -zv <host> 173

Block it in the firewall

sudo ufw deny 173/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 173" -Direction Inbound -LocalPort 173 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 173 used for?

Port 173 is assigned by IANA to xyplex-mux (Xyplex).

Is port 173 TCP or UDP?

Port 173 is registered for TCP and UDP.

Is it safe to open port 173?

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 173 is open?

On Linux run "ss -ltnup 'sport = :173'", on macOS "lsof -nP -i :173", and on Windows "netstat -ano | findstr :173" to see the local process. From another machine, "nmap -p 173 <host>" shows whether it is reachable.

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