Linux tonic.o2switch.net 4.18.0-553.30.1.lve.el8.x86_64 #1 SMP Tue Dec 3 01:21:19 UTC 2024 x86_64

//lib/firewalld/services/mqtt.xml

 <?xml version="1.0" encoding="utf-8"?>
<service>
  <short>mqtt</short>
  <description>The Message Queuing Telemetry Transport (MQTT) is a machine-to-machine connectivity protocol. This variant of the protocol is unencrypted.</description>
  <port port="1883" protocol="tcp"/>
</service>