programowanie:python:mqtt [wiki.sases.pl]

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====== MQTT w Python ======
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Instalacja biblioteki: ''pip install paho-mqtt''\\
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===== Połączenie =====
<code python>
import random
import logging
from paho.mqtt import client as mqtt_client

logging.basicConfig(level=logging.INFO)

broker = '127.0.0.1'
port = 1883
# generate client ID with pub prefix randomly
client_id = f'python-mqtt-{random.randint(0, 100)}'
# username = 'username'
# password = 'password'

def connect_mqtt() -> mqtt_client:
    def on_connect(client, userdata, flags, rc):
        if rc == 0:
            logging.info("Connected to MQTT Broker!")
        else:
            logging.error(f"Failed to connect, return code {rc}")
            # Attempt to reconnect
            client.reconnect()

    client = mqtt_client.Client(client_id)
    # client.username_pw_set(username, password)
    client.on_connect = on_connect
    client.connect(broker, port)
    return client
</code>
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===== Subskrypcja =====
<code python>
def subscribe(client: mqtt_client, topics):
    def on_message(client, userdata, msg):
        logging.info(f"Received `{msg.payload.decode()}` from `{msg.topic}` topic")

    for topic in topics:
        client.subscribe(topic)
    client.on_message = on_message
</code>
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===== Publikacja =====
<code python> 
msg = f"message"
topic = 'topic/topic'
result = client.publish(topic, msg)
status = result[0]
if status == 0:
   logging.info(f"Send `{msg}` to topic `{topic}`")
else:
   logging.error(f"Failed to send message to topic {topic}")
</code>
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===== Pętla obsługująca MQTT =====

== Przykład 1: ==
<code python>
client.loop_start()

while True:
   pass

client.loop_stop()
</code>

== Przykład 2: ==
<code python>
while True:
    rc = client.loop(timeout=1.0)
    if rc != 0:
        # need to handle error, possible reconnecting or stopping the application
</code>