main.py

import paho.mqtt.client as mqtt  # necessary imports
from datetime import date, datetime
import json

# function to connect with topic
def on_connect(client, userdata, flags, rc):  # client method to connect

    if rc == 0:
        print("connected OK Returned code=", rc)  # let us know we connected to the broker

        # TOPICS MUST BE ADDED HERE
        client.subscribe("smarthouse/sensors/data")
        # topic
        # topic
        # topic
        # topic
        # topic

    else:
        print("Bad connection Returned code=", rc)  # if we can't connect

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# function to receive messages
def on_message(client, userdata, msg,):  # client method to get messages from topic
    topic = msg.topic  # for use when we can't decode

    try:
        day = date.today()  # date function call
        clock = datetime.now()  # time function calls
        time_time = datetime.time(clock)

        # DECODING CODE GOES HERE FOR EACH SEPARATE TOPIC
        if topic == "smarthouse/sensors/data":                   # decodes message from specific topic (sensors)
            data = json.loads(msg.payload.decode("utf-8"))       # decode message, turns it back into array 'data'
            # stores data from arrays to variables
            Id = data[0]                                         # example: database.Id = data[0]
            location = data[1]
            temperature = data[2]

        # print message with data, time and date to check if it is received and decoded
        print("Received message at : date-" + str(day) + " time-" + str(time_time) + " / data: topic: " + topic + ";  value: "
              + str(data))
        # shows that data is stored from array to variables (JUST FOR TESTING)
        print("Data stored at:  'Id'=" + str(Id) + "; 'location'=" + location + "; temperature=" + str(temperature))

    except:
        print("Cannot decode data on topic:" + topic)  # cannot decode; print the topic for the non-decodable message

# define client
client = mqtt.Client()

# callback functions
client.on_connect = on_connect
client.on_message = on_message

client.connect("broker.hivemq.com", 1883)  # connect to the broker on an appropriate port

client.loop_forever()  # keep looping forever (allows realtime subscription)