Connect devices to IoT

Trimble IoT manages device communication through a message broker. Devices publish messages to a message broker and also subscribe to messages that the message broker publishes.

Prerequisites:

• Activate device in IoT, refer to Activate Devices.

Information needed to connect to Trimble IoT and manage device communication

• Host Address: Broker endpoint. This host address can be found in the Groups API response
• Port: MQTT listens on 8883
• Protocol: MQTT
• CA: Server certificate of the Broker endpoint. Click here to download the Server Certificate.
• Key: Private Key of the Device Certificate.
• Cert: Device Certificate of the device (PEM formatted).
• ClientId: Unique identifier for a device. It can be found in the device activate response. For more details refer to the Devices API.

Code sample

Tip

1. Install Python
2. Save code sample as a python file.
3. Install dependencies. i.e, pip install paho-mqtt==1.6.1
4. Replace below values in the code sample
   • <D2C Topic> with actual D2C topic. i.e., devices/{{clientId}}/messages/events/ Example Topic: devices/637b62aa-aa61-4e51-a657-42ca393929b7/messages/events/
   • <ClientId> with actual client id. Client Id is the device profile id and will have been provided in Device activation response. It can later be acquired using GET Device API request. Example client id: 637b62aa-aa61-4e51-a657-42ca393929b7
   • <Group BrokerEndpoint> with the actual broker endpoint. Broken endpoint will have been provided in the Group activation response. It can later be acquired using GET Group API request. Example client id: test.azure-devices.net
   • <Server CA path> with the actual relative path of Server CA - DigiCertGlobalRootG2. Example server ca path: caPath = r"C:\DeviceTesting\Scripts\azureservercatest.pem"
   • <Operational Certificate Path> with the actual relative path of Device Certificate path. Example certificate path: certPath = r"C:\DeviceTesting\Scripts\device1.pem"
   • <Operational Private key Path> with the actual relative path of Device Private key path. Example private key path: keyPath = r"C:\DeviceTesting\Scripts\device1.key"
   • <Device Username> with actual Device Username. Device Username will have been provided in Device activation response. It can later be acquired using GET Device API request. i.e., {{BrokerEndpoint}}/{{clientId}}/?api-version=2021-04-12 Example Topic: test.azure-devices.net/637b62aa-aa61-4e51-a657-42ca393929b7/?api-version=2021-04-12
   • <cloud to device message topic> with actual C2D topic. i.e., devices/{{clientId}}/messages/devicebound/# Example Topic: devices/637b62aa-aa61-4e51-a657-42ca393929b7/messages/devicebound/#
5. Execute Python filename.py

import paho.mqtt.client as paho
import os
import socket
import ssl
from time import sleep
from random import uniform
import json

import logging
logging.basicConfig(level=logging.DEBUG)

# Refactored original source - https://github.com/mariocannistra/python-paho-mqtt-for-aws-iot

class PubSub(object):

    def __init__(self, listener = False, topic = "default"):
        self.connect = False
        self.listener = listener
        self.topic = topic
        self.logger = logging.getLogger(repr(self))

    def on_connect(self, client, userdata, flags, rc):
        print("Device connected with result code: " + str(rc))
        self.mqttc.subscribe("<cloud to device message topic>", qos=1)

    def __on_message(self, client, userdata, msg):
        self.logger.info("{0}, {1} - {2}".format(userdata, msg.topic, msg.payload))

    def __on_log(self, client, userdata, level, buf):
        self.logger.debug("{0}, {1}, {2}, {3}".format(client, userdata, level, buf))

    def on_disconnect(self, client, userdata, rc):
        print("Device disconnected with result code: " + str(rc))

    def on_publish(self,client,userdata, mid):
        print("Device sent message")

    def on_subscribe(self,client, userdata, mid, granted_qos):
     print("Client Subscribed")

    def bootstrap_mqtt(self):

        self.mqttc = paho.Client(client_id="<ClientId>")
        self.mqttc.on_connect = self.on_connect
        self.mqttc.on_message = self.__on_message
        self.mqttc.on_publish= self.on_publish
        self.mqttc.on_subscribe = self.on_subscribe
        self.mqttc.on_log = self.__on_log
        self.mqttc.on_disconnect = self.on_disconnect

        azurehost = "<Group BrokerEndpoint>"
        azureport = 8883

        caPath = "<Server CA path>"
        certPath = "<Operational Certificate Path>"
        keyPath = "<Operational Private key Path>"

        self.mqttc.tls_set(ca_certs=caPath, certfile=certPath, keyfile=keyPath,
               cert_reqs=ssl.CERT_NONE, tls_version=ssl.PROTOCOL_TLSv1_2, ciphers=None)

        self.mqttc.username_pw_set(username='<Device Username>')
        result_of_connection = self.mqttc.connect(azurehost, azureport, keepalive=120)

        if result_of_connection == 0:
            self.connect = True

        return self

    def start(self):
        self.mqttc.loop_start()

        while True:
            sleep(2)
            if self.connect == True:
                print('Waiting for disconnect')
                self.mqttc.publish('<D2C Topic>', json.dumps({'data':'test'}), qos=1)
            else:
                self.logger.debug("Attempting to connect.")

if __name__ == '__main__':
    PubSub(listener = True).bootstrap_mqtt().start()