Simple example of MQTT subscriber using paho.mqtt and SSL Client Authentification for AWS Iot Core

ssl_client_authn_mqtt_subscriber.py

import sys
import ssl
import time
import datetime
import json
import logging, traceback
import paho.mqtt.client as mqtt

IoT_protocol_name = "x-amzn-mqtt-ca"
aws_iot_endpoint = "XXXXXXXXXX-ats.iot.us-west-2.amazonaws.com" # <random>.iot.<region>.amazonaws.com
url = "https://{}".format(aws_iot_endpoint)

ca = "/IoTMailboxPLP/certs/CA/VeriSign-Class-3-Public-Primary-Certification-Authority-G5.pem.crt"
cert = "/IoTMailboxPLP/certs/CERT/certificate.pem.crt"
private = "/IoTMailboxPLP/certs/KEY/private.pem.key"

MQTT_TOPIC = "thing/IoTMailboxPLP"

logger = logging.getLogger()
logger.setLevel(logging.DEBUG)
handler = logging.StreamHandler(sys.stdout)
log_format = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
handler.setFormatter(log_format)
logger.addHandler(handler)

def ssl_alpn():
    try:
        #debug print opnessl version
        logger.info("open ssl version:{}".format(ssl.OPENSSL_VERSION))
        ssl_context = ssl.create_default_context()
        ssl_context.set_alpn_protocols([IoT_protocol_name])
        ssl_context.load_verify_locations(cafile=ca)
        ssl_context.load_cert_chain(certfile=cert, keyfile=private)

        return  ssl_context
    except Exception as e:
        print("exception ssl_alpn()")
        raise e

# Define on connect event function
# We shall subscribe to our Topic in this function
def on_connect(mosq, obj, flags, rc):
        print "Connected!"
        mqttc.subscribe(MQTT_TOPIC, 0)

# Define on_message event function.
# This function will be invoked every time,
# a new message arrives for the subscribed topic
def on_message(mosq, obj, msg):
        print "Topic: " + str(msg.topic)
        print "QoS: " + str(msg.qos)
        print "Payload: " + str(msg.payload)

def on_subscribe(mosq, obj, mid, granted_qos):
    print("Subscribed to Topic: " +
        MQTT_TOPIC + " with QoS: " + str(granted_qos))


mqttc = mqtt.Client()
ssl_context= ssl_alpn()
mqttc.tls_set_context(context=ssl_context)
# Assign event callbacks
mqttc.on_message = on_message
mqttc.on_connect = on_connect
mqttc.on_subscribe = on_subscribe

logger.info("start connect")
mqttc.connect(aws_iot_endpoint, port=443)
logger.info("connect success")

# Continue monitoring the incoming messages for subscribed topic
mqttc.loop_forever()