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// Other services

Port 4373: Remote Authenticated Command Service

Port 4373 is assigned by IANA to remctl (Remote Authenticated Command Service).

4373

How remctl works

Other services
client:4373remctlresponse client:4373remctlresponse

The client sends a request to port 4373 and the remctl 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 4373 dangerous?

We have no specific security note for port 4373. 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 4373

ServicePortTransportDescriptionReferenceUpdated
remctl 4373 TCP, UDP Remote Authenticated Command Service - 2007-08-30

// source: IANA service name and port number registry

03 Check it

Which program uses port 4373, and is it reachable?

Linux

sudo ss -ltnup 'sport = :4373'      # process listening on 4373
sudo lsof -nP -i :4373

macOS

sudo lsof -nP -i :4373

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 4373 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 4373
netstat -ano | findstr :4373

From another machine

nmap -p 4373 -sV <host>
sudo nmap -sU -p 4373 <host>
nc -zv <host> 4373

Block it in the firewall

sudo ufw deny 4373/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 4373" -Direction Inbound -LocalPort 4373 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 4373 used for?

Port 4373 is assigned by IANA to remctl (Remote Authenticated Command Service).

Is port 4373 TCP or UDP?

Port 4373 is registered for TCP and UDP.

Is it safe to open port 4373?

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 4373 is open?

On Linux run "ss -ltnup 'sport = :4373'", on macOS "lsof -nP -i :4373", and on Windows "netstat -ano | findstr :4373" to see the local process. From another machine, "nmap -p 4373 <host>" shows whether it is reachable.

05 Related
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