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// Other services

Port 1729: CityNL License Management

Port 1729 is assigned by IANA to citynl (CityNL License Management).

1729

How citynl works

Other services
client:1729citynlresponse client:1729citynlresponse

The client sends a request to port 1729 and the citynl 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 1729 dangerous?

We have no specific security note for port 1729. 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 1729

ServicePortTransportDescriptionReferenceUpdated
citynl 1729 TCP, UDP CityNL License Management - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 1729, and is it reachable?

Linux

sudo ss -ltnup 'sport = :1729'      # process listening on 1729
sudo lsof -nP -i :1729

macOS

sudo lsof -nP -i :1729

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 1729 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 1729
netstat -ano | findstr :1729

From another machine

nmap -p 1729 -sV <host>
sudo nmap -sU -p 1729 <host>
nc -zv <host> 1729

Block it in the firewall

sudo ufw deny 1729/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 1729" -Direction Inbound -LocalPort 1729 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 1729 used for?

Port 1729 is assigned by IANA to citynl (CityNL License Management).

Is port 1729 TCP or UDP?

Port 1729 is registered for TCP and UDP.

Is it safe to open port 1729?

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 1729 is open?

On Linux run "ss -ltnup 'sport = :1729'", on macOS "lsof -nP -i :1729", and on Windows "netstat -ano | findstr :1729" to see the local process. From another machine, "nmap -p 1729 <host>" shows whether it is reachable.

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