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iotc - Azure IoT Central - Python (light) device SDK Documentation

Prerequisites

Python 2.7+ or Python 3.4+ or Micropython 1.9+

Runtime dependencies vary per platform

Install

Python 2/3

pip install iotc

Common Concepts

  • API calls should return 0 on success and error code otherwise.
  • External API naming convention follows lowerCamelCase for Device class members

Usage

import iotc
device = iotc.Device(scopeId, keyORCert, deviceId, credType)
  • scopeId : Azure IoT DPS Scope Id
  • keyORcert : Symmetric key or x509 Certificate
  • deviceId : Device Id
  • credType : IOTConnectType.IOTC_CONNECT_SYMM_KEY or IOTConnectType.IOTC_CONNECT_X509_CERT

keyORcert for X509 certificate:

credType = IOTConnectType.IOTC_CONNECT_X509_CERT
keyORcert = {
  "keyfile": "/src/python/test/device.key.pem",
  "certfile": "/src/python/test/device.cert.pem"
}

keyORcert for SAS token:

credType = IOTConnectType.IOTC_CONNECT_SYMM_KEY
keyORcert = "xxxxxxxxxxxxxxx........"

setLogLevel

set logging level

device.setLogLevel(logLevel)

logLevel : (default value is IOTC_LOGGING_DISABLED)

class IOTLogLevel:
  IOTC_LOGGING_DISABLED =  1
  IOTC_LOGGING_API_ONLY =  2
  IOTC_LOGGING_ALL      = 16

i.e. => device.setLogLevel(IOTLogLevel.IOTC_LOGGING_API_ONLY)

setExitOnError

enable/disable application termination on mqtt later exceptions. (default false)

device.setExitOnError(isEnabled)

i.e. => device.setExitOnError(True)

setModelData

set the device model data (if any)

device.setModelData(modelJSON)

modelJSON : Device model definition.

i.e. => device.setModelData({"iotcModelId":"PUT_MODEL_ID_HERE"})

setTokenExpiration

set the token expiration timeout. default is 21600 seconds (6 hours)

device.setTokenExpiration(totalSeconds)

totalSeconds : timeout in seconds.

i.e. => device.setTokenExpiration(600)

setServiceHost

set the service endpoint URL

device.setServiceHost(url)

url : URL for service endpoint. (default value is global.azure-devices-provisioning.net)

call this before connect

setQosLevel

Set the MQTT Quality of Service (QoS) level desired for all MQTT publish calls

device.setQosLevel(qosLevel)

qosLevel : (default value is IOTC_QOS_AT_MOST_ONCE)

class IOTQosLevel:
  IOTC_QOS_AT_MOST_ONCE  = 0
  IOTC_QOS_AT_LEAST_ONCE = 1

Note: IOTC_QOS_AT_LEAST_ONCE will have slower performance than IOTC_QOS_AT_MOST_ONCE as the MQTT client must store the value for possible replay and also wait for an acknowledgement from the IoT Hub that the MQTT message has been received. Think of IOTC_QOS_AT_MOST_ONCE as "fire and forget" vs. IOTC_QOS_AT_LEAST_ONCE as "guaranteed delivery". As the developer you should consider the importance of 100% data delivery vs. increased connection time and data traffic over the data connection.

call this before connect

connect

connect device client # blocking. Raises ConnectionStatus event.

device.connect()

or

device.connect(hostName)

i.e. => device.connect()

sendTelemetry

send telemetry

device.sendTelemetry(payload, [[optional system properties]])

payload : A text payload.

i.e. => device.sendTelemetry('{ "temperature": 15 }')

You may also set system properties for the telemetry message. See also iothub message format

i.e. => device.sendTelemetry('{ "temperature":22 }', {"iothub-creation-time-utc": time.time()})

sendState

send device state

device.sendState(payload)

payload : A text payload.

i.e. => device.sendState('{ "status": "WARNING"}')

sendProperty

send reported property

device.sendProperty(payload)

payload : A text payload.

i.e. => device.sendProperty('{"countdown":{"value": %d}}')

doNext

let framework do the partial MQTT work.

device.doNext()

isConnected

returns whether the connection was established or not.

device.isConnected()

i.e. => device.isConnected()

disconnect

disconnect device client

device.disconnect()

i.e. => device.disconnect()

getDeviceSettings

pulls latest twin data (device properties). Raises SettingsUpdated event.

device.getDeviceSettings()

i.e. => device.getDeviceSettings()

getHostName

returns the iothub hostname cached during the initial connection.

device.getHostName()

i.e. => device.getDeviceHostName()

on

set event callback to listen events

  • ConnectionStatus : connection status has changed
  • MessageSent : message was sent
  • Command : a command received from Azure IoT Central
  • SettingsUpdated : device settings were updated

i.e.

def onconnect(info):
  if info.getStatusCode() == 0:
    print("connected!")

device.on("ConnectionStatus", onconnect)

def onmessagesent(info):
  print("message sent -> " + info.getPayload())

device.on("MessageSent", onmessagesent)

def oncommand(info):
  print("command name:", info.getTag())
  print("command args: ", info.getPayload())

device.on("Command", oncommand)

def onsettingsupdated(info):
  print("setting name:", info.getTag())
  print("setting value: ", info.getPayload())

device.on("SettingsUpdated", onsettingsupdated)

callback info class

iotc callbacks have a single argument derived from IOTCallbackInfo. Using this interface, you can get the callback details and respond back when it's necessary.

public members of IOTCallbackInfo are;

getResponseCode() : get response code or None

getResponseMessage() : get response message or None

setResponse(responseCode, responseMessage) : set callback response

i.e. => info.setResponse(200, 'completed')

getClient() : get active device client

getEventName() : get the name of the event

getPayload() : get the payload or None

getTag() : get the tag or None

getStatusCode() : get callback status code

sample app

import iotc
from iotc import IOTConnectType, IOTLogLevel

deviceId = "DEVICE_ID"
scopeId = "SCOPE_ID"
deviceKey = "DEVICE_KEY"

# see iotc.Device documentation above for x509 argument sample
iotc = iotc.Device(scopeId, deviceKey, deviceId, IOTConnectType.IOTC_CONNECT_SYMM_KEY)
iotc.setLogLevel(IOTLogLevel.IOTC_LOGGING_API_ONLY)
iotc.setQosLevel(IOTQosLevel.IOTC_QOS_AT_MOST_ONCE)

gCanSend = False
gCounter = 0

def onconnect(info):
  global gCanSend
  print("- [onconnect] => status:" + str(info.getStatusCode()))
  if info.getStatusCode() == 0:
     if iotc.isConnected():
       gCanSend = True

def onmessagesent(info):
  print("\t- [onmessagesent] => " + str(info.getPayload()))

def oncommand(info):
  print("command name:", info.getTag())
  print("command value: ", info.getPayload())

def onsettingsupdated(info):
  print("setting name:", info.getTag())
  print("setting value: ", info.getPayload())

iotc.on("ConnectionStatus", onconnect)
iotc.on("MessageSent", onmessagesent)
iotc.on("Command", oncommand)
iotc.on("SettingsUpdated", onsettingsupdated)

iotc.connect()

while iotc.isConnected():
  iotc.doNext() # do the async work needed to be done for MQTT
  if gCanSend == True:
    if gCounter % 20 == 0:
      gCounter = 0
      print("Sending telemetry..")
      iotc.sendTelemetry("{\"temp\": " + str(randint(20, 45)) + "}")

    gCounter += 1