AWS IoT SDK for JavaScript

The aws-iot-device-sdk.js package allows developers to write JavaScript applications which access the AWS IoT Platform via MQTT or MQTT over the Secure WebSocket Protocol. It can be used in Node.js environments as well as in browser applications.

• Overview
• Installation
• Examples
• API Documentation
• Connection Types
• Example Programs
• Browser Applications
• Troubleshooting
• Unit Tests
• License
• Support

Overview

This document provides instructions on how to install and configure the AWS IoT device SDK for JavaScript, and includes examples demonstrating use of the SDK APIs.

MQTT Connection

This package is built on top of mqtt.js and provides two classes: 'device' and 'thingShadow'. The 'device' class wraps mqtt.js to provide a secure connection to the AWS IoT platform and expose the mqtt.js interfaces upward. It provides features to simplify handling of intermittent connections, including progressive backoff retries, automatic re-subscription upon connection, and queued offline publishing with configurable drain rate.

Thing Shadows

The 'thingShadow' class implements additional functionality for accessing Thing Shadows via the AWS IoT API; the thingShadow class allows devices to update, be notified of changes to, get the current state of, or delete Thing Shadows from AWS IoT. Thing Shadows allow applications and devices to synchronize their state on the AWS IoT platform. For example, a remote device can update its Thing Shadow in AWS IoT, allowing a user to view the device's last reported state via a mobile app. The user can also update the device's Thing Shadow in AWS IoT and the remote device will synchronize with the new state. The 'thingShadow' class supports multiple Thing Shadows per mqtt connection and allows pass-through of non-Thing-Shadow topics and mqtt events.

Installation

Installing with npm:

npm install aws-iot-device-sdk

Installing from github:

git clone https://github.com/aws/aws-iot-device-sdk-js.git
cd aws-iot-device-sdk-js
npm install

Examples

Device Class

var awsIot = require('aws-iot-device-sdk');

//
// Replace the values of '<YourUniqueClientIdentifier>' and '<YourAWSRegion>'
// with a unique client identifier and the AWS region you created your
// certificate in (e.g. 'us-east-1').  NOTE: client identifiers must be
// unique within your AWS account; if a client attempts to connect with a
// client identifier which is already in use, the existing connection will
// be terminated.
//
var device = awsIot.device({
   keyPath: <YourPrivateKeyPath>,
  certPath: <YourCertificatePath>,
    caPath: <YourRootCACertificatePath>,
  clientId: <YourUniqueClientIdentifier>,
    region: <YourAWSRegion> 
});

//
// Device is an instance returned by mqtt.Client(), see mqtt.js for full
// documentation.
//
device
  .on('connect', function() {
    console.log('connect');
    device.subscribe('topic_1');
    device.publish('topic_2', JSON.stringify({ test_data: 1}));
    });

device
  .on('message', function(topic, payload) {
    console.log('message', topic, payload.toString());
  });

Thing Shadow Class

var awsIot = require('aws-iot-device-sdk');

//
// Replace the values of '<YourUniqueClientIdentifier>' and '<YourAWSRegion>'
// with a unique client identifier and the AWS region you created your
// certificate in (e.g. 'us-east-1').  NOTE: client identifiers must be
// unique within your AWS account; if a client attempts to connect with a
// client identifier which is already in use, the existing connection will
// be terminated.
//
var thingShadows = awsIot.thingShadow({
   keyPath: <YourPrivateKeyPath>,
  certPath: <YourCertificatePath>,
    caPath: <YourRootCACertificatePath>,
  clientId: <YourUniqueClientIdentifier>,
    region: <YourAWSRegion>
});

//
// Client token value returned from thingShadows.update() operation
//
var clientTokenUpdate;

//
// Simulated device values
//
var rval = 187;
var gval = 114;
var bval = 222;

thingShadows.on('connect', function() {
//
// After connecting to the AWS IoT platform, register interest in the
// Thing Shadow named 'RGBLedLamp'.
//
    thingShadows.register( 'RGBLedLamp' );
//
// 5 seconds after registering, update the Thing Shadow named 
// 'RGBLedLamp' with the latest device state and save the clientToken
// so that we can correlate it with status or timeout events.
//
// Note that the delay is not required for subsequent updates; only
// the first update after a Thing Shadow registration using default
// parameters requires a delay.  See API documentation for the update
// method for more details.
//
    setTimeout( function() {
//
// Thing shadow state
//
       var rgbLedLampState = {"state":{"desired":{"red":rval,"green":gval,"blue":bval}}};

       clientTokenUpdate = thingShadows.update('RGBLedLamp', rgbLedLampState  );
//
// The update method returns a clientToken; if non-null, this value will
// be sent in a 'status' event when the operation completes, allowing you
// to know whether or not the update was successful.  If the update method
// returns null, it's because another operation is currently in progress and
// you'll need to wait until it completes (or times out) before updating the 
// shadow.
//
       if (clientTokenUpdate === null)
       {
          console.log('update shadow failed, operation still in progress');
       }
       }, 5000 );
    });

thingShadows.on('status', 
    function(thingName, stat, clientToken, stateObject) {
       console.log('received '+stat+' on '+thingName+': '+
                   JSON.stringify(stateObject));
//
// These events report the status of update(), get(), and delete() 
// calls.  The clientToken value associated with the event will have
// the same value which was returned in an earlier call to get(),
// update(), or delete().  Use status events to keep track of the
// status of shadow operations.
//
    });

thingShadows.on('delta', 
    function(thingName, stateObject) {
       console.log('received delta on '+thingName+': '+
                   JSON.stringify(stateObject));
    });

thingShadows.on('timeout',
    function(thingName, clientToken) {
       console.log('received timeout on '+thingName+
                   ' with token: '+ clientToken);
//
// In the event that a shadow operation times out, you'll receive
// one of these events.  The clientToken value associated with the
// event will have the same value which was returned in an earlier
// call to get(), update(), or delete().
//
    });

## API Documentation

• awsIot.device()
• awsIot.thingShadow()
• awsIot.thingShadow#register()
• awsIot.thingShadow#unregister()
• awsIot.thingShadow#update()
• awsIot.thingShadow#get()
• awsIot.thingShadow#delete()
• awsIot.thingShadow#publish()
• awsIot.thingShadow#subscribe()
• awsIot.thingShadow#unsubscribe()
• awsIot.thingShadow#end()

---

awsIot.device(options)

Returns a wrapper for the mqtt.Client() class, configured for a TLS connection with the AWS IoT platform and with arguments as specified in options. The AWSIoT-specific arguments are as follows:

• region: the AWS IoT region you will operate in (default 'us-east-1')
• clientId: the client ID you will use to connect to AWS IoT
• certPath: path of the client certificate file
• keyPath: path of the private key file associated with the client certificate
• caPath: path of your CA certificate file
• clientCert: same as certPath, but can also accept a buffer containing client certificate data
• privateKey: same as keyPath, but can also accept a buffer containing private key data
• caCert: same as caPath, but can also accept a buffer containing CA certificate data
• autoResubscribe: set to 'true' to automatically re-subscribe to topics after reconnection (default 'true')
• offlineQueueing: set to 'true' to automatically queue published messages while offline (default 'true')
• offlineQueueMaxSize: enforce a maximum size for the offline message queue (default 0, e.g. no maximum)
• offlineQueueDropBehavior: set to 'oldest' or 'newest' to define drop behavior on a full queue when offlineQueueMaxSize > 0
• drainTimeMs: the minimum time in milliseconds between publishes when draining after reconnection (default 250)
• baseReconnectTimeMs: the base reconnection time in milliseconds (default 1000)
• maximumReconnectTimeMs: the maximum reconnection time in milliseconds (default 128000)
• minimumConnectionTimeMs: the minimum time in milliseconds that a connection must be maintained in order to be considered stable (default 20000)
• protocol: the connection type, either 'mqtts' (default) or 'wss' (WebSocket/TLS). Note that when set to 'wss', values must be provided for the Access Key ID and Secret Key in either the following options or in environment variables as specified in WebSocket Configuration.
• websocketOptions: if protocol is set to 'wss', you can use this parameter to pass additional options to the underlying WebSocket object; these options are documented here.
• accessKeyId: used to specify the Access Key ID when protocol is set to 'wss'. Overrides the environment variable AWS_ACCESS_KEY_ID if set.
• secretKey: used to specify the Secret Key when protocol is set to 'wss'. Overrides the environment variable AWS_SECRET_ACCESS_KEY if set.
• sessionToken: (required when authenticating via Cognito, optional otherwise) used to specify the Session Token when protocol is set to 'wss'. Overrides the environment variable AWS_SESSION_TOKEN if set.

All certificates and keys must be in PEM format.

options also contains arguments specific to mqtt. See [the mqtt client documentation] (https://github.com/mqttjs/MQTT.js/blob/master/README.md#client) for details of these arguments.

Supports all events emitted by the mqtt.Client() class.

awsIot.device#updateWebSocketCredentials(accessKeyId, secretKey, sessionToken, expiration)

Update the credentials set used to authenticate via WebSocket/SigV4. This method is designed to be invoked during the callback of the getCredentialsForIdentity method in the AWS SDK for JavaScript.

• accessKeyId: the latest Access Key to use when connecting via WebSocket/SigV4
• secretKey: the latest Secret Key to use when connecting via WebSocket/SigV4
• sessionToken: the latest Session Token to use when connecting via WebSocket/SigV4
• expiration: the time this credentials set will expire

---

awsIot.thingShadow(options)

The thingShadow class wraps an instance of the device class with additional functionality to operate on Thing Shadows via the AWS IoT API. The arguments in options include all those in the device class, with the addition of the following arguments specific to the thingShadow class:

• operationTimeout: the timeout for thing operations (default 10 seconds)

Supports all events emitted by the mqtt.Client() class; however, the semantics for the message event are slightly different and additional events are available as described below:

Event 'message'

function(topic, message) {}

Emitted when a message is received on a topic not related to any Thing Shadows:

• topic topic of the received packet
• message payload of the received packet

Event 'status'

function(thingName, stat, clientToken, stateObject) {}

Emitted when an operation update|get|delete completes.

• thingName name of the Thing Shadow for which the operation has completed
• stat status of the operation accepted|rejected
• clientToken the operation's clientToken
• stateObject the stateObject returned for the operation

Applications can use clientToken values to correlate status events with the operations that they are associated with by saving the clientTokens returned from each operation.

Event 'delta'

function(thingName, stateObject) {}

Emitted when a delta has been received for a registered Thing Shadow.

• thingName name of the Thing Shadow that has received a delta
• stateObject the stateObject returned for the operation

Event 'foreignStateChange'

function(thingName, operation, stateObject) {}

Emitted when a different client's update or delete operation is accepted on the shadow.

• thingName name of the Thing Shadow for which the operation has completed
• operation operation performed by the foreign client update|delete
• stateObject the stateObject returned for the operation

This event allows an application to be aware of successful update or delete operations performed by different clients.

Event 'timeout'

function(thingName, clientToken) {}

Emitted when an operation update|get|delete has timed out.

• thingName name of the Thing Shadow that has received a timeout
• clientToken the operation's clientToken

Applications can use clientToken values to correlate timeout events with the operations that they are associated with by saving the clientTokens returned from each operation.

---

awsIot.thingShadow#register(thingName, [options] )

Register interest in the Thing Shadow named thingName. The thingShadow class will subscribe to any applicable topics, and will fire events for the Thing Shadow until awsIot.thingShadow#unregister() is called with thingName. options can contain the following arguments to modify how this Thing Shadow is processed:

• ignoreDeltas: set to true to not subscribe to the delta sub-topic for this Thing Shadow; used in cases where the application is not interested in changes (e.g. update only.) (default false)
• persistentSubscribe: set to false to unsubscribe from all operation sub-topics while not performing an operation (default true)
• discardStale: set to false to allow receiving messages with old version numbers (default true)
• enableVersioning: set to true to send version numbers with shadow updates (default true)

The persistentSubscribe argument allows an application to get faster operation responses at the expense of potentially receiving more irrelevant response traffic (i.e., response traffic for other clients who have registered interest in the same Thing Shadow). When persistentSubscribe is set to false, operation sub-topics are only subscribed to during the scope of that operation; note that in this mode, update, get, and delete operations will be much slower; however, the application will be less likely to receive irrelevant response traffic.

The discardStale argument allows applications to receive messages which have obsolete version numbers. This can happen when messages are received out-of-order; applications which set this argument to false should use other methods to determine how to treat the data (e.g. use a time stamp property to know how old/stale it is).

If enableVersioning is set to true, version numbers will be sent with each operation. AWS IoT maintains version numbers for each shadow, and will reject operations which contain the incorrect version; in applications where multiple clients update the same shadow, clients can use versioning to avoid overwriting each other's changes.

---

awsIot.thingShadow#unregister(thingName)

Unregister interest in the Thing Shadow named thingName. The thingShadow class will unsubscribe from all applicable topics and no more events will be fired for thingName.

---

awsIot.thingShadow#update(thingName, stateObject)

Update the Thing Shadow named thingName with the state specified in the JavaScript object stateObject. thingName must have been previously registered using awsIot.thingShadow#register(). The thingShadow class will subscribe to all applicable topics and publish stateObject on the update sub-topic.

This function returns a clientToken, which is a unique value associated with the update operation. When a 'status' or 'timeout' event is emitted, the clientToken will be supplied as one of the parameters, allowing the application to keep track of the status of each operation. The caller may create their own clientToken value; if stateObject contains a clientToken property, that will be used rather than the internally generated value. Note that it should be of atomic type (i.e. numeric or string). This function returns 'null' if an operation is already in progress.

---

awsIot.thingShadow#get(thingName, [clientToken])

Get the current state of the Thing Shadow named thingName, which must have been previously registered using awsIot.thingShadow#register(). The thingShadow class will subscribe to all applicable topics and publish on the get sub-topic.

This function returns a clientToken, which is a unique value associated with the get operation. When a 'status or 'timeout' event is emitted, the clientToken will be supplied as one of the parameters, allowing the application to keep track of the status of each operation. The caller may supply their own clientToken value (optional); if supplied, the value of clientToken will be used rather than the internally generated value. Note that this value should be of atomic type (i.e. numeric or string). This function returns 'null' if an operation is already in progress.

---

awsIot.thingShadow#delete(thingName, [clientToken])

Delete the Thing Shadow named thingName, which must have been previously registered using awsIot.thingShadow#register(). The thingShadow class will subscribe to all applicable topics and publish on the delete sub-topic.

This function returns a clientToken, which is a unique value associated with the delete operation. When a 'status' or 'timeout' event is emitted, the clientToken will be supplied as one of the parameters, allowing the application to keep track of the status of each operation. The caller may supply their own clientToken value (optional); if supplied, the value of clientToken will be used rather than the internally generated value. Note that this value should be of atomic type (i.e. numeric or string). This function returns 'null' if an operation is already in progress.

---

awsIot.thingShadow#publish(topic, message, [options], [callback])

Identical to the mqtt.Client#publish() method, with the restriction that the topic may not represent a Thing Shadow. This method allows the user to publish messages to topics on the same connection used to access Thing Shadows.

---

awsIot.thingShadow#subscribe(topic, [options], [callback])

Identical to the mqtt.Client#subscribe() method, with the restriction that the topic may not represent a Thing Shadow. This method allows the user to subscribe to messages from topics on the same connection used to access Thing Shadows.

---

awsIot.thingShadow#unsubscribe(topic, [options], [callback])

Identical to the mqtt.Client#unsubscribe() method, with the restriction that the topic may not represent a Thing Shadow. This method allows the user to unsubscribe from topics on the same used to access Thing Shadows.

---

awsIot.thingShadow#end([force], [callback])

Invokes the mqtt.Client#end() method on the MQTT connection owned by the thingShadow class. The force and callback parameters are optional and identical in function to the parameters in the mqtt.Client#end() method.

Connection Types

This SDK supports two types of connections to the AWS IoT platform:

• MQTT over TLS with mutual certificate authentication using port 8883
• MQTT over WebSocket/TLS with SigV4 authentication using port 443

The default connection type is MQTT over TLS with mutual certificate authentication; to configure a WebSocket/TLS connection, set the protocol option to wss when instantiating the awsIot.device() or awsIot.thingShadow() classes.

Example Programs

The 'examples' directory contains several programs which demonstrate usage of the AWS IoT APIs:

• device-example.js: demonstrate simple MQTT publish and subscribe operations.

• echo-example.js: test Thing Shadow operation by echoing all delta state updates to the update topic; used in conjunction with the AWS IoT Console to verify connectivity with the AWS IoT platform.

• thing-example.js: use a Thing Shadow to automatically synchronize state between a simulated device and a control application.

• thing-passthrough-example.js: demonstrate use of a Thing Shadow with pasthrough of standard MQTT publish and subscribe messages.

• temperature-control/temperature-control.js: an interactive device simulation which uses Thing Shadows.

The example programs use command line parameters to set options. To see the available options, run the program and specify the '-h' option as follows:

node examples/<EXAMPLE-PROGRAM> -h

NOTE: If you didn't create your certificate in the default region ('us-east-1'), you'll need to specify the region (e.g., 'us-west-2') that you created your certificate in. When using the example programs, this can be done with the '-g' command line option.

WebSocket Configuration

The example programs can be configured to use a WebSocket/TLS connection to the AWS IoT platform by adding '--protocol=wss' to the command line to override the default setting of 'mqtts'.

  -P, --protocol=PROTOCOL          connect using PROTOCOL (mqtts|wss)

When using a WebSocket/TLS connection, you'll need to set the following environment variables:

  export AWS_ACCESS_KEY_ID=[a valid AWS access key ID]
  export AWS_SECRET_ACCESS_KEY=[a valid AWS secret access key]

The values of AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY must contain valid AWS Identity and Access Management (IAM) credentials. For more information about AWS IAM, visit the AWS IAM home page.

Certificate Configuration

When not configured to use a WebSocket/TLS connection, the example programs require a client certificate and private key (created using either the AWS IoT Console or the AWS IoT CLI) in order to authenticate with AWS IoT. Each example program uses command line options to specify the names and/or locations of certificates as follows:

Specify a directory containing default-named certificates

  -f, --certificate-dir=DIR        look in DIR for certificates

The --certificate-dir (-f) option will read all certificate and key files from the directory specified. Default certificate/key file names are as follows:

• certificate.pem.crt: your AWS IoT certificate
• private.pem.key: the private key associated with your AWS IoT certificate
• root-CA.crt: the root CA certificate (available from Symantec here)

Specify certificate names and locations individually

  -k, --private-key=FILE           use FILE as private key
  -c, --client-certificate=FILE    use FILE as client certificate
  -a, --ca-certificate=FILE        use FILE as CA certificate

The '-f' (certificate directory) option can be combined with these so that you don't have to specify absolute pathnames for each file.

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Use a configuration file