Bash

Connecting to Azure IoT Central via HTTP (bash/curl/node)

If you want to jump directly to example script without the explanations, click here

DEVICE_ID="ENTER DEVICE ID HERE"
DEVICE_KEY="ENTER DEVICE SYM KEY HERE"
SCOPE="ENTER SCOPE ID HERE"
MESSAGE='{"temp":15}' # <=== your telemetry goes here

Open apps.azureiotcentral.com > Device Explorer (explorer) > Select one of the templates (i.e. MXCHIP) > Click to + button on the tab > Select Real device

You should see a Connect link on top-right of the device page. Once you click to that button, you will find all the DEVICE_ID, DEVICE_KEY (Primary_key) and SCOPE_ID there.

Now, we need to generate the authentication header for our requests. Please take a look at the basic BASH function below. It executes a node script and uses the arguments we collected from the device page.

function getAuth {
  # A node script that prints an auth signature using SCOPE, DEVICE_ID and DEVICE_KEY
  AUTH=`node -e "\
  const crypto   = require('crypto');\

  function computeDrivedSymmetricKey(masterKey, regId) {\
    return crypto.createHmac('SHA256', Buffer.from(masterKey, 'base64'))\
      .update(regId, 'utf8')\
      .digest('base64');\
  }\
  \
  var expires = parseInt((Date.now() + (7200 * 1000)) / 1000);\
  var sr = '${SCOPE}%2f${TARGET}%2f${DEVICE_ID}';\
  var sigNoEncode = computeDrivedSymmetricKey('${DEVICE_KEY}', sr + '\n' + expires);\
  var sigEncoded = encodeURIComponent(sigNoEncode);\
  console.log('SharedAccessSignature sr=' + sr + '&sig=' + sigEncoded + '&se=' + expires)\
  "`
}

SCOPEID="$SCOPE"
TARGET="registrations"
# get auth for Azure IoT DPS service
getAuth

We will make the first DPS call. This call will provide us the operationId

# use the Auth and make a PUT request to Azure IoT DPS service
curl \
  -H "authorization: ${AUTH}&skn=registration" \
  -H 'content-type: application/json; charset=utf-8' -H 'content-length: 25' \
  -s -o output.txt \
  --request PUT --data "{\"registrationId\":\"$DEVICE_ID\"}" "https://global.azure-devices-provisioning.net/$SCOPEID/registrations/$DEVICE_ID/register?api-version=2018-11-01"

OPERATION=`node -e "fs=require('fs');c=fs.readFileSync('./output.txt')+'';c=JSON.parse(c);if(c.errorCode){console.log(c);process.exit(1);}console.log(c.operationId)"`

if [[ $? != 0 ]]; then
  # if there was an error, print the stdout part and exit
  echo "$OPERATION"
  exit
else
  echo "Authenticating.."
  # wait 2 secs before making the GET request to Azure IoT DPS service
  # the second call will bring us the Azure IoT Hub endpoint we are supposed to talk
  sleep 2

Now, we are going to make the second DPS call. This call will give us the Azure IoT hub hostname. Using that hostname and our device key, we will create the authentication key for our iothub telemetry message.

  OUT=`curl -s \
  -H "authorization: ${AUTH}&skn=registration" \
  -H "content-type: application/json; charset=utf-8" \
  --request GET "https://global.azure-devices-provisioning.net/$SCOPEID/registrations/$DEVICE_ID/operations/$OPERATION?api-version=2018-11-01"`

  # parse the return value from the DPS host and try to grab the assigned hub
  OUT=`node -pe "a=JSON.parse('$OUT');if(a.errorCode){a}else{a.registrationState.assignedHub}"`

  if [[ $OUT =~ 'errorCode' ]]; then
    # if there was an error, print the stdout part and exit
    echo "$OUT"
    exit
  fi

Finally generate the Azure IoT hub authentication key using the hostname that we received from DPS.

  TARGET="devices"
  SCOPE="$OUT"
  # get Auth for Azure IoThub service
  getAuth

  echo "OK"
  echo

It's time to send our telemetry to Azure IoT Hub

  echo "SENDING => " $MESSAGE

  # send a telemetry to Azure IoT hub service
  curl -s \
  -H "authorization: ${AUTH}" \
  -H "iothub-to: /devices/$DEVICE_ID/messages/events" \
  --request POST --data "$MESSAGE" "https://$SCOPE/devices/$DEVICE_ID/messages/events/?api-version=2016-11-14"

  echo "DONE"
fi

echo

Turn back to Azure IoT central and browse the device page. You should see temperature telemetry soon.