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// Other services

Port 4591: HRPD L3T (AT-AN)

Port 4591 is assigned by IANA to l3t-at-an (HRPD L3T (AT-AN)).

4591

How l3t-at-an works

Other services
client:4591l3t-at-anresponse client:4591l3t-at-anresponse

The client sends a request to port 4591 and the l3t-at-an 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 4591 dangerous?

We have no specific security note for port 4591. 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 4591

ServicePortTransportDescriptionReferenceUpdated
l3t-at-an 4591 TCP, UDP HRPD L3T (AT-AN) - 2009-02-27

// source: IANA service name and port number registry

03 Check it

Which program uses port 4591, and is it reachable?

Linux

sudo ss -ltnup 'sport = :4591'      # process listening on 4591
sudo lsof -nP -i :4591

macOS

sudo lsof -nP -i :4591

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 4591 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 4591
netstat -ano | findstr :4591

From another machine

nmap -p 4591 -sV <host>
sudo nmap -sU -p 4591 <host>
nc -zv <host> 4591

Block it in the firewall

sudo ufw deny 4591/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 4591" -Direction Inbound -LocalPort 4591 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 4591 used for?

Port 4591 is assigned by IANA to l3t-at-an (HRPD L3T (AT-AN)).

Is port 4591 TCP or UDP?

Port 4591 is registered for TCP and UDP.

Is it safe to open port 4591?

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 4591 is open?

On Linux run "ss -ltnup 'sport = :4591'", on macOS "lsof -nP -i :4591", and on Windows "netstat -ano | findstr :4591" to see the local process. From another machine, "nmap -p 4591 <host>" shows whether it is reachable.

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