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// Other services

Port 3693: Emergency Automatic Structure Lockdown System

Port 3693 is assigned by IANA to easl (Emergency Automatic Structure Lockdown System).

3693

How easl works

Other services
client:3693easlresponse client:3693easlresponse

The client sends a request to port 3693 and the easl service answers.

Transport
TCP
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 3693 dangerous?

We have no specific security note for port 3693. 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 3693

ServicePortTransportDescriptionReferenceUpdated
easl 3693 TCP Emergency Automatic Structure Lockdown System - 2014-11-26
-3693-Reserved--

// source: IANA service name and port number registry

03 Check it

Which program uses port 3693, and is it reachable?

Linux

sudo ss -ltnup 'sport = :3693'      # process listening on 3693
sudo lsof -nP -i :3693

macOS

sudo lsof -nP -i :3693

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 3693 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 3693
netstat -ano | findstr :3693

From another machine

nmap -p 3693 -sV <host>
nc -zv <host> 3693

Block it in the firewall

sudo ufw deny 3693/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 3693" -Direction Inbound -LocalPort 3693 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 3693 used for?

Port 3693 is assigned by IANA to easl (Emergency Automatic Structure Lockdown System).

Is port 3693 TCP or UDP?

Port 3693 is registered for TCP.

Is it safe to open port 3693?

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 3693 is open?

On Linux run "ss -ltnup 'sport = :3693'", on macOS "lsof -nP -i :3693", and on Windows "netstat -ano | findstr :3693" to see the local process. From another machine, "nmap -p 3693 <host>" shows whether it is reachable.

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