MQTT: Connection to Azure IoT Hub (Micropython)

Question

I'm unable to connect to Azure IoT Hub using the umqtt.simple2 library with SSL using MicroPython v1.22.2.

from umqtt.simple2 import MQTTClient

HUB_HOSTNAME = "AzureIoTHubHostName"
PORT = 8883
CLIENT_ID = "DeviceId"
USERNAME = f"{HUB_HOSTNAME}/{CLIENT_ID}/?api-version=2021-04-12"
PASSWORD = "SASToken"
TOPIC = f"devices/{CLIENT_ID}/messages/events/"
MESSAGE = b"Hello Azure IoT Hub!"
CADATA_PATH = "cadata_path"

with open(CADATA_PATH, "rb") as f:
    cadata = f.read()

ssl_params = {"cert_reqs": ussl.CERT_NONE, "cadata": cadata}

client = MQTTClient(
    CLIENT_ID,
    HUB_HOSTNAME,
    port=PORT,
    user=USERNAME,
    password=PASSWORD,
    ssl=True,
    ssl_params=ssl_params,
)

client.connect()

client.publish(TOPIC, MESSAGE)

client.disconnect()

No error message is provided by the connect method, making it difficult to diagnose the issue further (it fails on line 267 in simple2, when wrapping the socket --> self.sock = ussl.wrap_socket(self.sock_raw, **self.ssl_params))

I have tested my certificate file with openssl to check if the handshake occurs (openssl s_client -connect), and it works ok.

Could anyone advise on how to resolve this connectivity issue with Azure IoT Hub using MicroPython? Any guidance would be greatly appreciated.

Answer 1

The code below is used to connect a device to Azure IoT Hub using MQTT with Python. It sets up a connection to Azure IoT Hub using the umqtt.simple2 library and publishes some telemetry data.

• I followed IoTMQTTSample python
• MicroPython on ESP32 sends telemetry to Azure IoT Hub with MQTT.

IOT_HUB_NAME = "{iothub_name}"
IOT_HUB_DEVICE_ID = "{device_id}"
IOT_HUB_SAS_TOKEN = "{sas_token}"

def on_connect(client, userdata, flags, rc):
    print("connect: " + str(rc))

def on_publish(client, userdata, mid):
    print("publish: " + str(mid))

# Create an MQTT client instance
mqtt_client = MQTTClient(client_id=IOT_HUB_DEVICE_ID, server=IOT_HUB_NAME + ".azure-devices.net", port=8883)

# Set the connection callback
mqtt_client.on_connect = on_connect

# Set the publish callback
mqtt_client.on_publish = on_publish

# Set username and password
mqtt_client.username_pw_set(username=IOT_HUB_NAME + ".azure-devices.net/" + IOT_HUB_DEVICE_ID + "/?api-version=2021-04-12", 
                            password=IOT_HUB_SAS_TOKEN)

messages = ["Accio", "Aguamenti", "Alarte Ascendare", "Expecto Patronum", "Homenum Revelio"]
for i in range(len(messages)):
    print("sending message[" + str(i) + "]: " + messages[i])
    mqtt_client.publish("devices/" + IOT_HUB_DEVICE_ID + "/messages/events/", payload=messages[i], qos=1)

• Connect to Azure IoT Hub using MQTT

az iot hub generate-sas-token --connection-string  "HostName=<your-hub-name>.azure-devices.net;DeviceId=<your-device-id>;SharedAccessKey=<your-shared-access-key>"

Output: