MQTT subscribe

[pentadom]

Hello,

I'm trying to subscribe to a MQTT topic ("arqueta/humedad") and asign his value to an object of logic machine.

I'm using de test Mosquitto broker and I publish previously a value to the topic "arqueta/humedad".

I'm using this code (extracted from here) as a resident script but It seems doesn't works and I don't know what I'm doing wrong...

Code:

-- Define a function which is called by mqtt_client:handler(),
-- whenever messages are received on the subscribed topics

    function callback(topic, message)
    print("Received: " .. topic .. ": " .. message)
    if (message == "quit") then running = false end
  end

-- Create an MQTT client instance, connect to the MQTT server and
-- subscribe to the topic called "arqueta/humedad"

    MQTT = require("mosquitto")
  MQTT.Utility.set_debug(true)
    mqtt_client = MQTT.client.create("https://test.mosquitto.org", 1883, callback)
    mqtt_client:connect("logicmachine")
    local humedad = mqtt_client:subscribe("arqueta/humedad")
    grp.update('1/1/27', humedad)


-- Continously invoke mqtt_client:handler() to process the MQTT protocol and
-- handle any received messages.  Also, publish a message on topic "test/1"

  running = true

  while (running) do
    mqtt_client:handler()
    mqtt_client:publish("test/1", "test message")
    socket.sleep(1.0)  -- seconds
  end

-- Clean-up by unsubscribing from the topic and closing the MQTT connection

  mqtt_client:unsubscribe({"arqueta/humedad"})
  mqtt_client:destroy()