Mosquitto debian, NodeJS mqtt

https://www.digitalocean.com/community/tutorials/how-to-install-and-secure-the-mosquitto-mqtt-messaging-broker-on-debian-9
http://www.steves-internet-guide.com/topic-restriction-mosquitto-configuration/
=========
MOSQUITTO
=========
Install
-------
$ sudo apt update
$ sudo apt install mosquitto mosquitto-clients
--------------------------
Configure password and SSL
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$ sudo mosquitto_passwd -c /etc/mosquitto/passwd sammy
$ sudo nano /etc/mosquitto/conf.d/default.conf
allow_anonymous false
password_file /etc/mosquitto/passwd
acl_file /etc/mosquitto/aclfile
listener 1883 localhost
listener 8883
certfile /etc/letsencrypt/live/mqtt.example.com/cert.pem
cafile /etc/letsencrypt/live/mqtt.example.com/chain.pem
keyfile /etc/letsencrypt/live/mqtt.example.com/privkey.pem
$ sudo nano /etc/mosquitto/aclfile
#anonymous user
topic read $SYS/#
#user sammy (#=any topic)
user sammy
topic readwrite #
#all client (%c = client id, %u = user)
pattern readwrite %u/#
$ sudo ufw allow 8883
$ sudo systemctl restart mosquitto
$ mosquitto_sub -h mqtt.example.com -p 8883 --capath /etc/ssl/certs/ -t "test/topic" -u "sammy" -P "password"
$ mosquitto_pub -h mqtt.example.com -p 8883 --capath /etc/ssl/certs/ -t "test/topic" -m "hello world" -u "sammy" -P "password"

https://stackoverflow.com/questions/62299097/nodejs-connect-to-mqtt-server-with-credentials-and-ssl
------
NodeJS
------
$ npm install mqtt --save
const mqtt = require( 'mqtt' )
const fs = require( 'fs' )
const client = new mqtt.connect( 'mqtts://' + SERVERNAME, {
  rejectUnauthorized: false,
  username: SERVERUSERNAME,
  password: SERVERPASSWORD,
  // port: 8883
  connectTimeout: 5000,
  ca: [ fs.readFileSync( MYCAFILENAME ) ],
  cert: fs.readFileSync( MYCERTFILENAME ),
  key: fs.readFileSync( MYKEYFILENAME )
} )
client.on( 'connect', () => {
    console.log( 'connected' )
    client.subscribe( TOPIC, ( err ) => {
      console.log( 'subscribed' )
      if ( ! err ) {
        client.publish( TOPIC, "hello world" )
      }
    } )
} )
client.on( 'message', function( topic, msg ){
    console.log( msg.toString() )
    client.end()
} )