require 'mqtt'
require 'json'

HOST = '192.168.x.x'
PORT = 1883

MQTT::Client.connect(remote_host: HOST, remote_port: PORT, username: 'test', password: 'test') do |client|
  client.get('test') do |topic, message|
    data = JSON.parse(message)
    puts "#{topic}: #{data}.class = #{data.class}"
  end
end