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Adds token refresh to MQTT example. (GoogleCloudPlatform#1197)
* Adds token refresh to MQTT example. * Fixes lint error.
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‎iot/api-client/mqtt_example/README.md‎

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‎iot/api-client/mqtt_example/README.rst‎

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.. This file is automatically generated. Do not edit this file directly.
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Google Cloud IoT Core API Python Samples
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===============================================================================
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This directory contains samples for Google Cloud IoT Core API. `Google Cloud IoT Core`_ allows developers to easily integrate Publish and Subscribe functionality with devices and programmatically manage device authorization.
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The following example runs the sample using the project ID `blue-jet-123` and the device name `my-python-device`:
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python cloudiot_mqtt_example.py \
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--registry_id=my-registry \
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--project_id=blue-jet-123 \
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--device_id=my-python-device \
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--algorithm=RS256 \
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--private_key_file=../rsa_private.pem
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.. _Google Cloud IoT Core API: https://cloud.google.com/iot/docs
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Setup
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-------------------------------------------------------------------------------
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Install Dependencies
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++++++++++++++++++++
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#. Install `pip`_ and `virtualenv`_ if you do not already have them. You may want to refer to the `Python Development Environment Setup Guide`_ for Google Cloud Platform for instructions.
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.. _Python Development Environment Setup Guide:
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https://cloud.google.com/python/setup
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#. Create a virtualenv. Samples are compatible with Python 2.7 and 3.4+.
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.. code-block:: bash
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$ virtualenv env
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$ source env/bin/activate
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#. Install the dependencies needed to run the samples.
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.. code-block:: bash
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$ pip install -r requirements.txt
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.. _pip: https://pip.pypa.io/
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.. _virtualenv: https://virtualenv.pypa.io/
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Samples
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-------------------------------------------------------------------------------
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MQTT Device Client Example
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+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
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To run this sample:
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.. code-block:: bash
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$ python cloudiot_mqtt_example.py
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usage: cloudiot_mqtt_example.py [-h] [--project_id PROJECT_ID] --registry_id
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REGISTRY_ID --device_id DEVICE_ID
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--private_key_file PRIVATE_KEY_FILE
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--algorithm {RS256,ES256}
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[--cloud_region CLOUD_REGION]
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[--ca_certs CA_CERTS]
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[--num_messages NUM_MESSAGES]
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[--message_type {event,state}]
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[--mqtt_bridge_hostname MQTT_BRIDGE_HOSTNAME]
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[--mqtt_bridge_port {8883,443}]
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[--jwt_expires_minutes JWT_EXPIRES_MINUTES]
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Example Google Cloud IoT Core MQTT device connection code.
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optional arguments:
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-h, --help show this help message and exit
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--project_id PROJECT_ID
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GCP cloud project name
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--registry_id REGISTRY_ID
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Cloud IoT Core registry id
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--device_id DEVICE_ID
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Cloud IoT Core device id
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--private_key_file PRIVATE_KEY_FILE
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Path to private key file.
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--algorithm {RS256,ES256}
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Which encryption algorithm to use to generate the JWT.
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--cloud_region CLOUD_REGION
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GCP cloud region
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--ca_certs CA_CERTS CA root from https://pki.google.com/roots.pem
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--num_messages NUM_MESSAGES
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Number of messages to publish.
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--message_type {event,state}
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Indicates whether the message to be published is a
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telemetry event or a device state message.
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--mqtt_bridge_hostname MQTT_BRIDGE_HOSTNAME
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MQTT bridge hostname.
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--mqtt_bridge_port {8883,443}
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MQTT bridge port.
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--jwt_expires_minutes JWT_EXPIRES_MINUTES
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Expiration time, in minutes, for JWT tokens.
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.. _Google Cloud SDK: https://cloud.google.com/sdk/

‎iot/api-client/mqtt_example/README.rst.in‎

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# This file is used to generate README.rst
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product:
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name: Google Cloud IoT Core API
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short_name: Cloud IoT Core
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url: https://cloud.google.com/iot/docs
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description: >
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`Google Cloud IoT Core`_ allows developers to easily integrate Publish and
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Subscribe functionality with devices and programmatically manage device
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authorization.
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The following example runs the sample using the project ID `blue-jet-123`
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and the device name `my-python-device`:
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python cloudiot_mqtt_example.py \
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--registry_id=my-registry \
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--project_id=blue-jet-123 \
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--device_id=my-python-device \
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--algorithm=RS256 \
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--private_key_file=../rsa_private.pem
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setup:
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- install_deps
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samples:
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- name: MQTT Device Client Example
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file: cloudiot_mqtt_example.py
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show_help: True
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cloud_client_library: false

‎iot/api-client/mqtt_example/cloudiot_mqtt_example.py‎

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import jwt
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import paho.mqtt.client as mqtt
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# [START iot_mqtt_jwt]
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def create_jwt(project_id, private_key_file, algorithm):
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"""Creates a JWT (https://jwt.io) to establish an MQTT connection.
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return jwt.encode(token, private_key, algorithm=algorithm)
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# [END iot_mqtt_jwt]
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# [START iot_mqtt_config]
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def error_str(rc):
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"""Convert a Paho error to a human readable string."""
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return '{}: {}'.format(rc, mqtt.error_string(rc))
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print('on_publish')
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def get_client(
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project_id, cloud_region, registry_id, device_id, private_key_file,
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algorithm, ca_certs, mqtt_bridge_hostname, mqtt_bridge_port):
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"""Create our MQTT client. The client_id is a unique string that identifies
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this device. For Google Cloud IoT Core, it must be in the format below."""
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client = mqtt.Client(
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client_id=('projects/{}/locations/{}/registries/{}/devices/{}'
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.format(
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project_id,
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cloud_region,
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registry_id,
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device_id)))
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# With Google Cloud IoT Core, the username field is ignored, and the
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# password field is used to transmit a JWT to authorize the device.
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client.username_pw_set(
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username='unused',
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password=create_jwt(
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project_id, private_key_file, algorithm))
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# Enable SSL/TLS support.
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client.tls_set(ca_certs=ca_certs)
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# Register message callbacks. https://eclipse.org/paho/clients/python/docs/
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# describes additional callbacks that Paho supports. In this example, the
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# callbacks just print to standard out.
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client.on_connect = on_connect
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client.on_publish = on_publish
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client.on_disconnect = on_disconnect
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# Connect to the Google MQTT bridge.
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client.connect(mqtt_bridge_hostname, mqtt_bridge_port)
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# Start the network loop.
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client.loop_start()
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return client
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# [END iot_mqtt_config]
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def parse_command_line_args():
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"""Parse command line arguments."""
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parser = argparse.ArgumentParser(description=(
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default=8883,
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type=int,
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help='MQTT bridge port.')
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parser.add_argument(
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'--jwt_expires_minutes',
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default=20,
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type=int,
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help=('Expiration time, in minutes, for JWT tokens.'))
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return parser.parse_args()
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# [START iot_mqtt_run]
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def main():
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args = parse_command_line_args()
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# Create our MQTT client. The client_id is a unique string that identifies
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# this device. For Google Cloud IoT Core, it must be in the format below.
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client = mqtt.Client(
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client_id=('projects/{}/locations/{}/registries/{}/devices/{}'
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.format(
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args.project_id,
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args.cloud_region,
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args.registry_id,
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args.device_id)))
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# With Google Cloud IoT Core, the username field is ignored, and the
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# password field is used to transmit a JWT to authorize the device.
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client.username_pw_set(
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username='unused',
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password=create_jwt(
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args.project_id, args.private_key_file, args.algorithm))
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# Enable SSL/TLS support.
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client.tls_set(ca_certs=args.ca_certs)
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# Register message callbacks. https://eclipse.org/paho/clients/python/docs/
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# describes additional callbacks that Paho supports. In this example, the
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# callbacks just print to standard out.
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client.on_connect = on_connect
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client.on_publish = on_publish
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client.on_disconnect = on_disconnect
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# Connect to the Google MQTT bridge.
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client.connect(args.mqtt_bridge_hostname, args.mqtt_bridge_port)
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# Start the network loop.
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client.loop_start()
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# Publish to the events or state topic based on the flag.
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sub_topic = 'events' if args.message_type == 'event' else 'state'
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mqtt_topic = '/devices/{}/{}'.format(args.device_id, sub_topic)
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jwt_iat = datetime.datetime.utcnow()
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jwt_exp_mins = args.jwt_expires_minutes
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client = get_client(
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args.project_id, args.cloud_region, args.registry_id, args.device_id,
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args.private_key_file, args.algorithm, args.ca_certs,
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args.mqtt_bridge_hostname, args.mqtt_bridge_port)
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# Publish num_messages mesages to the MQTT bridge once per second.
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for i in range(1, args.num_messages + 1):
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payload = '{}/{}-payload-{}'.format(
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args.registry_id, args.device_id, i)
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print('Publishing message {}/{}: \'{}\''.format(
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i, args.num_messages, payload))
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seconds_since_issue = (datetime.datetime.utcnow() - jwt_iat).seconds
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if seconds_since_issue > 60 * jwt_exp_mins:
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print('Refreshing token after {}s').format(seconds_since_issue)
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client.loop_stop()
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jwt_iat = datetime.datetime.utcnow()
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client = get_client(
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args.project_id, args.cloud_region,
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args.registry_id, args.device_id, args.private_key_file,
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args.algorithm, args.ca_certs, args.mqtt_bridge_hostname,
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args.mqtt_bridge_port)
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# Publish "payload" to the MQTT topic. qos=1 means at least once
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# delivery. Cloud IoT Core also supports qos=0 for at most once
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# delivery.
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# End the network loop and finish.
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client.loop_stop()
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print('Finished.')
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# [END iot_mqtt_run]
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if __name__ == '__main__':

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