aws-mqtt-websockets

Implementation of a middleware to use AWS MQTT service through websockets. Aiming the esp8266 platform

ChangeLog

• 1.1.0 - can use AWS STS temporary credentials - change some dynamic to static memory allocation to avoid memory fragmentation
• 1.0.1 - works with arduinoWebSockets v.2.0.5 and arduino/esp sdk 2.3.0
• 1.0.alpha - stable - works with arduinoWebSockets v.2.0.2 and arduino/esp sdk 2.1.0
• 0.3 - own impl of circular buffer
• 0.2 - auto reconnection
• 0.1 - has known limitation and it was not extensively tested

Motivation

As we cannot use AWS MQTT service directly because of the lack of support for TLS 1.2, we need to use the websocket communication as a transport layer for MQTT through SSL (supported by esp8266)

This way we can change the state of your esp8266 devices in realtime, without using the AWS Restful API and busy-waiting inefficient approach.

Dependencies

Library	Link	Use
aws-sdk-arduino	https://github.com/odelot/aws-sdk-arduino	aws signing functions
arduinoWebSockets	https://github.com/Links2004/arduinoWebSockets	websocket comm impl
Paho MQTT for Arduino	https://projects.eclipse.org/projects/technology.paho/downloads	mqtt comm impl

Installation

1. Configure your arduino ide to compile and upload programs to ESP8266 (Arduino core for ESP8266 - details https://github.com/esp8266/Arduino )**
2. Install all the dependencies as Arduino Libraries
3. Install aws-mqtt-websockets as Arduino Library as well
4. Configure the example file with your AWS credencials and endpoints
5. Compile, upload and run!

** The library was tested with 2.3.0 stable version of Arduino core for ESP8266

Limitation

• need to be stress tested
• may work in Arduino out of AWS environment (turn off SSL and set Path)

Usage

It is transparent. It is the same as the usage of Paho. There is just some changes in the connection step. See the example for details. Things you should edit in the example:

• ssid and password to connect to wifi
• domain/endpoint for your aws iot service
• region of your aws iot service
• aws user key **
• aws user secret key

** It is a good practice creating a new user (and grant just iot services permission). Avoid use the key/secret key of your main aws console user

//AWS IOT config, change these:
char wifi_ssid[]       = "your-ssid";
char wifi_password[]   = "your-password";
char aws_endpoint[]    = "your-endpoint.iot.eu-west-1.amazonaws.com";
char aws_key[]         = "your-iam-key";
char aws_secret[]      = "your-iam-secret-key";
char aws_region[]      = "eu-west-1";
const char* aws_topic  = "$aws/things/your-device/shadow/update";
int port = 443;

//MQTT config
const int maxMQTTpackageSize = 128;
const int maxMQTTMessageHandlers = 1;

AWS STS Temporary Credential

To avoid having a long term credential hardcoded in our device, you can create temporary credentials that will last up to 36 hours using the AWS STS service (learn more here http://docs.aws.amazon.com/IAM/latest/UserGuide/id_credentials_temp_request.html).

Using STS you will get a AWS key, AWS secret and AWS token. To inform the AWS token, use the following method

//it is just an example. As the credential last up to 36 hours, you will need to get temporary credential every 36 hours
//you won't use it hard coded
char token[] = 'FQoDYXdzEHgaDN7ZQSxqszH+LgBTXCKsAeU5dsW/g3BK01wyYoBk0vnCfz+D19w2kslSC5drDXyN9Nxx14WcgrOOWNxHsLRDPkcrYhw6DIkW1Nvv1mKu3i86riq19qhBose7v1XngRLBQwgfU/HnlIzJegNEEGgeMAkX0ErF77WfV2pxCzF6ZMRv7kn+a6yE2LURLg/M8eq3lYoyQcJFq55JfVPVUIpx/avEsjgCR/MvlHXlhtJqviClB3mRlvwBcz4vpq4ogpKnzAU=';
awsWSclient.setAWSToken (token);