Using gateways with the MQTT bridge

// const deviceId = `myDevice`;
// const gatewayId = `mygateway`;
// const registryId = `myRegistry`;
// const projectId = `my-project-123`;
// const region = `us-central1`;
// const algorithm = `RS256`;
// const privateKeyFile = `./rsa_private.pem`;
// const serverCertFile = `./roots.pem`;
/**
 * @see https://clearblade.atlassian.net/wiki/spaces/IC/pages/2210299905/Retargeting+Devices#Production-URL-%2F-URLs for full list of URLs
 */
// const mqttBridgeHostname = `us-central1-mqtt.clearblade.com`;
// const mqttBridgePort = 8883;
// const clientDuration = 60000;

const mqttClientId = `projects/${projectId}/locations/${region}/registries/${registryId}/devices/${gatewayId}`;
console.log(mqttClientId);
const connectionArgs = {
  host: mqttBridgeHostname,
  port: mqttBridgePort,
  clientId: mqttClientId,
  username: "unused",
  password: createJwt(projectId, privateKeyFile, algorithm),
  protocol: "mqtts",
  qos: 1,
  secureProtocol: "TLSv1_2_method",
  ca: [readFileSync(serverCertFile)],
};

// Create a client, and connect to the ClearBlade MQTT bridge.
const client = mqtt.connect(connectionArgs);

client.on("connect", (success) => {
  if (!success) {
    console.log("Client not connected...");
  } else {
    setTimeout(() => {
      // Subscribe to gateway error topic.
      client.subscribe(`/devices/${gatewayId}/errors`, { qos: 0 });

      attachDevice(deviceId, client);

      setTimeout(() => {
        console.log("Closing connection to MQTT. Goodbye!");
        client.end(true);
      }, clientDuration); // Safely detach device and close connection.
    }, 5000);
  }
});

client.on("close", () => {
  console.log("Connection closed");
  shouldBackoff = true;
});

client.on("error", (err) => {
  console.log("error", err);
});

client.on("message", (topic, message) => {
  const decodedMessage = Buffer.from(message, "base64").toString("ascii");

  console.log(`message received on error topic ${topic}: ${decodedMessage}`);
});

client.on("packetsend", () => {
  // Logging packet send is very verbose
});

import time
import datetime
import ssl
import jwt
import random
import paho.mqtt.client as mqtt

# The initial backoff time after a disconnection occurs, in seconds.
minimum_backoff_time = 1

# The maximum backoff time before giving up, in seconds.
MAXIMUM_BACKOFF_TIME = 32

# Whether to wait with exponential backoff before publishing.
should_backoff = False

def create_jwt(project_id, private_key_file, algorithm):
  """Creates a JWT (https://jwt.io) to establish an MQTT connection.
  Args:
    project_id: The cloud project ID this device belongs to
    private_key_file: A path to a file containing an RSA256 or
            ES256 private key.
    algorithm: The encryption algorithm to use (RS256 or ES256)
  Returns:
      A JWT generated from the given project_id and private key, which
      expires in 20 minutes. After 20 minutes, your client will be
      disconnected, and a new JWT will have to be generated.
  Raises:
      ValueError: If the private_key_file does not contain a known key.
  """

  token = {
    # The time that the token was issued at
    "iat": datetime.datetime.now(tz=datetime.timezone.utc),
    # The time the token expires.
    "exp": datetime.datetime.now(tz=datetime.timezone.utc) + datetime.timedelta(minutes=20),
    # The audience field should always be set to the GCP project id.
    "aud": project_id,
  }

  # Read the private key file.
  with open(private_key_file, "r") as f:
    private_key = f.read()

  print(
    "Creating JWT using {} from private key file {}".format(
      algorithm, private_key_file
    )
  )

  return jwt.encode(token, private_key, algorithm=algorithm)

def error_str(rc):
  """Convert a Paho error to a human readable string."""
  return "{}: {}".format(rc, mqtt.error_string(rc))


def on_connect(unused_client, unused_userdata, unused_flags, rc):
  """Callback for when a device connects."""
  print("on_connect", mqtt.connack_string(rc))

  # After a successful connect, reset backoff time and stop backing off.
  global should_backoff
  global minimum_backoff_time
  should_backoff = False
  minimum_backoff_time = 1


def on_disconnect(unused_client, unused_userdata, rc):
  """Paho callback for when a device disconnects."""
  print("on_disconnect", error_str(rc))

  # Since a disconnect occurred, the next loop iteration will wait with
  # exponential backoff.
  global should_backoff
  should_backoff = True


def on_publish(unused_client, unused_userdata, unused_mid):
  """Paho callback when a message is sent to the broker."""
  print("on_publish")


def on_message(unused_client, unused_userdata, message):
  """Callback when the device receives a message on a subscription."""
  payload = str(message.payload.decode("utf-8"))
  print(
    "Received message '{}' on topic '{}' with Qos {}".format(
      payload, message.topic, str(message.qos)
    )
  )


def attach_device(client, device_id, auth):
    """Attach the device to the gateway."""
    # [START iot_attach_device]
    attach_topic = "/devices/{}/attach".format(device_id)
    attach_payload = '{{"authorization" : "{}"}}'.format(auth)
    client.publish(attach_topic, attach_payload, qos=1)
    # [END iot_attach_device]


def detach_device(client, device_id):
    """Detach the device from the gateway."""
    # [START iot_detach_device]
    detach_topic = "/devices/{}/detach".format(device_id)
    print("Detaching: {}".format(detach_topic))
    client.publish(detach_topic, "{}", qos=1)
    # [END iot_detach_device]


def get_client(
  project_id,
  cloud_region,
  registry_id,
  device_id,
  private_key_file,
  algorithm,
  ca_certs,
  mqtt_bridge_hostname,
  mqtt_bridge_port,
):
  """Create our MQTT client. The client_id is a unique string that identifies
  this device. For Google Cloud IoT Core, it must be in the format below."""
  client_id = "projects/{}/locations/{}/registries/{}/devices/{}".format(
    project_id, cloud_region, registry_id, device_id
  )
  print("Device client_id is '{}'".format(client_id))

  client = mqtt.Client(client_id=client_id)

  # With Google Cloud IoT Core, the username field is ignored, and the
  # password field is used to transmit a JWT to authorize the device.
  client.username_pw_set(
    username="unused", password=create_jwt(project_id, private_key_file, algorithm)
  )

  # Enable SSL/TLS support.
  client.tls_set(ca_certs=ca_certs, tls_version=ssl.PROTOCOL_TLSv1_2)

  # Register message callbacks. https://eclipse.org/paho/clients/python/docs/
  # describes additional callbacks that Paho supports. In this example, the
  # callbacks just print to standard out.
  client.on_connect = on_connect
  client.on_publish = on_publish
  client.on_disconnect = on_disconnect
  client.on_message = on_message

  # Connect to the Google MQTT bridge.
  client.connect(mqtt_bridge_hostname, mqtt_bridge_port)

  # This is the topic that the device will receive configuration updates on.
  mqtt_config_topic = "/devices/{}/config".format(device_id)

  # Subscribe to the config topic.
  client.subscribe(mqtt_config_topic, qos=1)

  # The topic that the device will receive commands on.
  mqtt_command_topic = "/devices/{}/commands/#".format(device_id)

  # Subscribe to the commands topic, QoS 1 enables message acknowledgement.
  print("Subscribing to {}".format(mqtt_command_topic))
  client.subscribe(mqtt_command_topic, qos=0)

  return client


def listen_for_messages(
  service_account_json,
  project_id,
  cloud_region,
  registry_id,
  device_id,
  gateway_id,
  num_messages,
  private_key_file,
  algorithm,
  ca_certs,
  mqtt_bridge_hostname,
  mqtt_bridge_port,
  jwt_expires_minutes,
  duration,
  cb=None,
):
  """Listens for messages sent to the gateway and bound devices."""
  # [START iot_listen_for_messages]
  global minimum_backoff_time

  jwt_iat = datetime.datetime.now(tz=datetime.timezone.utc)
  jwt_exp_mins = jwt_expires_minutes
  # Use gateway to connect to server
  client = get_client(
    project_id,
    cloud_region,
    registry_id,
    gateway_id,
    private_key_file,
    algorithm,
    ca_certs,
    mqtt_bridge_hostname,
    mqtt_bridge_port,
  )

  attach_device(client, device_id, "")
  print("Waiting for device to attach.")
  time.sleep(5)

  # The topic devices receive configuration updates on.
  device_config_topic = "/devices/{}/config".format(device_id)
  client.subscribe(device_config_topic, qos=1)
  
  # The topic gateways receive configuration updates on.
  gateway_config_topic = "/devices/{}/config".format(gateway_id)
  client.subscribe(gateway_config_topic, qos=1)
  
  # The topic gateways receive error updates on. QoS must be 0.
  error_topic = "/devices/{}/errors".format(gateway_id)
  client.subscribe(error_topic, qos=0)
  
  # Wait about a minute for config messages.
  for i in range(1, duration):
    client.loop()
    
    if cb is not None:
      cb(client)

    if should_backoff:
      # If backoff time is too large, give up.
      if minimum_backoff_time > MAXIMUM_BACKOFF_TIME:
        print("Exceeded maximum backoff time. Giving up.")
        break

      delay = minimum_backoff_time + random.randint(0, 1000) / 1000.0
      time.sleep(delay)
      minimum_backoff_time *= 2
      client.connect(mqtt_bridge_hostname, mqtt_bridge_port)
    
    seconds_since_issue = (datetime.datetime.now(tz=datetime.timezone.utc) - jwt_iat).seconds
    if seconds_since_issue > 60 * jwt_exp_mins:
      print("Refreshing token after {}s".format(seconds_since_issue))
      jwt_iat = datetime.datetime.now(tz=datetime.timezone.utc)
      client = get_client(
        project_id,
        cloud_region,
        registry_id,
        gateway_id,
        private_key_file,
        algorithm,
        ca_certs,
        mqtt_bridge_hostname,
        mqtt_bridge_port,
      )
    
    time.sleep(1)

  detach_device(client, device_id)

  print("Finished.")
  # [END iot_listen_for_messages]



service_account_json = "/path/to/your/credentials.json"
project_id = "YOUR_PROJECT_ID"
cloud_region = "us-central1"
registry_id = "your-registry-id"
gateway_id = "your-gateway-id"
device_id = "your-test-device"

gateway_private_key_file = "/path/to/your/gateway/rsa_private.pem"
algorithm = "RS256"
ca_certs = "DigiCertGlobalRootCA.crt.pem"
mqtt_bridge_hostname = "us-central1-mqtt.clearblade.com"
mqtt_bridge_port = 8883

num_messages = 10
jwt_expires_minutes = 60
duration = 3

listen_for_messages(
  service_account_json,
  project_id,
  cloud_region,
  registry_id,
  device_id,
  gateway_id,
  num_messages,
  gateway_private_key_file,
  algorithm,
  ca_certs,
  mqtt_bridge_hostname,
  mqtt_bridge_port,
  jwt_expires_minutes,
  duration,
  cb=None,
)

string error_type;  // An error type's string description.
string device_id;   // The device ID that caused the error.
string description; // An error's description.

string message_type;  // The string MQTT message type.
string topic;  // The MQTT topic, if applicable; otherwise, it is empty.
int packet_id;  // The MQTT message's packet ID, if applicable; otherwise, it is zero.