MQTT

MQTT is a lightweight messaging protocol that is ideal for sending small packets of data to and from IoT devices via WiFi.

The broker used in this example is the IO Adafruit) platform, which is free and allows for tinkering with MQTT.

Visit IO Adafruit and create an account. You'll need to get hold of an API Key as well as your credentials. Visit this guide for more information about MQTT and how to use it with Adafruit's Broker.

This example will send a message to a topic on the Adafruit MQTT broker and then also subscribe to the same topic, in order to show how to use the subscribe functionality.

from mqtt import MQTTClient
from network import WLAN
import machine
import time

def sub_cb(topic, msg):
   print(msg)

wlan = WLAN(mode=WLAN.STA)
wlan.connect("yourwifinetwork", auth=(WLAN.WPA2, "wifipassword"), timeout=5000)

while not wlan.isconnected():  
    machine.idle()
print("Connected to WiFi\n")

client = MQTTClient("device_id", "io.adafruit.com",user="your_username", password="your_api_key", port=1883)

client.set_callback(sub_cb)
client.connect()
client.subscribe(topic="youraccount/feeds/lights")

while True:
    print("Sending ON")
    client.publish(topic="youraccount/feeds/lights", msg="ON")
    time.sleep(1)
    print("Sending OFF")
    client.publish(topic="youraccount/feeds/lights", msg="OFF")
    client.check_msg()

    time.sleep(1)