expressify-mqtt

expressify-mqtt

An Expressify strategy enabling RESTful application over an MQTT(S) transport.

Current version: 1.0.0

Lead Maintainer: Halim Qarroum

Table of contents

• Installation
• Features
• Usage
• Examples
• See also

Install

npm install --save expressify-mqtt

Features

• Natively supports the MQTT.js and the AWS IoT SDK librairies.
• Usage of an MQTT query-response pattern to optimize message exchanges and costs.
• Supports observation of resources using dedicated MQTT topics.
• Supports Node.js and the Browser (MQTT-over-Websockets).
• Automatically detects disconnected observers to stop emitting resource updates.

Usage

In order to use expressify-mqtt, you need to create an instance of the strategy using a backend such as MQTT.js or the AWS IoT SDK. The strategy requires that the MQTT backend follows the same interface as MQTT.js.

Creating a client

When initializing the expressify-mqtt strategy, you need to pass it a supported MQTT back-end, as well as a topic mountpoint indicating the base topic which the strategy will use to create its topic architecture.

// Injecting the `mqtt.js` library.
const mqtt = require('mqtt');

// Creating the client instance.
const client = new Expressify.Client({
  strategy: new MqttStrategy({ mqtt, topic: 'foo' })
});

Note that given the used MQTT service, there might be limitations on the number of forward slashes you can use.

Creating a server

The below example shows you how to create an instance of an Expressify server using the mqtt strategy.

// Injecting the `mqtt.js` library.
const mqtt = require('mqtt');

// Creating the server instance.
const server = new Expressify.Server({
  strategy: new MqttStrategy({ mqtt, topic: 'foo' })
});

// Listening for incoming requests.
server.listen().then(() => {
  console.log(`[+] The server is listening on mount point '${server.strategy.opts.topic}' !`);
});

Examples

Different functional examples involving the expressify-mqtt strategy are available in the examples directory.

See also

• The Expressify framework.
• The expressify-ipc strategy supporting local sockets.
• The expressify-pm strategy supporting .postMessage.