CloudMQTT

Last Updated: 12 November 2013

CloudMQTT is an add-on for providing a MQTT broker to your application(s).

MQTT is a lightweight pub/sub protocol, especially suited for low processor/bandwidth units like sensors and built-in system, but also suited for fast communication within applications.

CloudMQTT is exposed through the MQTT protocol for which there are supported client in Java, C, Python, Node.js, Ruby, Objective-C etc.

Provisioning the add-on

CloudMQTT can be attached to a Heroku application via the CLI:

$ heroku addons:add cloudmqtt
-----> Adding cloudmqtt to sharp-mountain-4005... done, v18 (free)

Once CloudMQTT has been added a CLOUDMQTT_URL setting will be available in the app configuration and will contain the canonical URL used to access the newly provisioned CloudMQTT service instance. This can be confirmed using the heroku config:get command.

$ heroku config:get CLOUDMQTT_URL
mqtt://user:pass@broker.cloudmqtt.com

After installing CloudMQTT the application should be configured to fully integrate with the add-on.

Local setup

Environment setup

After provisioning the add-on it’s necessary to locally replicate the config vars so your development environment can operate against the service.

Use Foreman to configure, run and manage process types specified in your app’s Procfile. Foreman reads configuration variables from an .env file. Use the following command to add the CLOUDMQTT_URL values retrieved from heroku config to .env.

$ heroku config -s | grep CLOUDMQTT_URL >> .env
$ more .env

Credentials and other sensitive configuration values should not be committed to source-control. In Git exclude the .env file with: echo .env >> .gitignore.

Service setup

A MQTT server can be installed for use in a local development environment. Typically this entails installing a MQTT compatible server like Mosquitto and pointing the CLOUDMQTT_URL to this local service.

curl http://repo.mosquitto.org/debian/mosquitto-repo.gpg.key | \
 apt-key add -
curl http://repo.mosquitto.org/debian/mosquitto-repo.list > \
 /etc/apt/sources.list.d/mosquitto-repo.list
apt-get update
apt-get install mosquitto

Your CLOUDMQTT_URL can then be subsituted with mqtt://localhost:1883.

Using with Ruby

Currently the most mature client library for Ruby is the synchronous ruby-mqtt, the async em-mqtt as yet to support user/password before it’s usable with CloudMQTT.

First you need to add mqtt as a dependency to your Gemfile and execute bundle install. In the following code snippet you can see you how can publish and subscribe. Note that the client is synchronous so you have to use threads if you want to subscribe and do other things at the same time.

require 'mqtt'
require 'uri'

# Create a hash with the connection parameters from the URL
uri = URI.parse ENV['CLOUDMQTT_URL'] || 'mqtt://localhost:1883'
conn_opts = {
  remote_host: uri.host,
  remote_port: uri.port,
  username: uri.user,
  password: uri.password,
}

Thread.new do
  MQTT::Client.connect(conn_opts) do |c|
    # The block will be called when you messages arrive to the topic
    c.get('test') do |topic, message|
      puts "#{topic}: #{message}"
    end
  end
end

MQTT::Client.connect(conn_opts) do |c|
  # publish a message to the topic 'test'
  loop do
    c.publish('test', 'Hello World')
    sleep 1
  end
end

Full sample code can be found here: github.com/CloudMQTT/ruby-mqtt-example

Worth noting is that the client does not yet support other QoS levels than 0, ie. no publish acknowledge or redelivery.

Using with Node.js

A good javascript MQTT library is MQTT.js. Add mqtt to your package.json file. Then a simple example could look like this:

var mqtt = require('mqtt'), url = require('url');
// Parse
var mqtt_url = url.parse(process.env.CLOUDMQTT_URL || 'mqtt://localhost:1883');
var auth = (mqtt_url.auth || ':').split(':');

// Create a client connection
var client = mqtt.createClient(mqtt_url.port, mqtt_url.hostname, {
  username: auth[0],
  password: auth[1]
});

client.on('connect', function() { // When connected

  // subscribe to a topic
  client.subscribe('hello/world', function() {
    // when a message arrives, do something with it
    client.on('message', function(topic, message, packet) {
      console.log("Received '" + message + "' on '" + topic + "'");
    });
  });

  // publish a message to a topic
  client.publish('hello/world', 'my message', function() {
    console.log("Message is published");
    client.end(); // Close the connection when published
  });
});

A full sample web app which uses MQTT.js, Express.js and SSE to deliver messages from and to a web browser is available here: github.com/CloudMQTT/mqtt-sse and can be tested out here at mqtt-sse.herokuapp.com.

Using with Python

The most feature complete MQTT client for Python is Mosquitto. Below you see an sample app which both publish and subscribes to CloudMQTT.

import mosquitto, os, urlparse

# Define event callbacks
def on_connect(mosq, obj, rc):
    print("rc: " + str(rc))

def on_message(mosq, obj, msg):
    print(msg.topic + " " + str(msg.qos) + " " + str(msg.payload))

def on_publish(mosq, obj, mid):
    print("mid: " + str(mid))

def on_subscribe(mosq, obj, mid, granted_qos):
    print("Subscribed: " + str(mid) + " " + str(granted_qos))

def on_log(mosq, obj, level, string):
    print(string)

mqttc = mosquitto.Mosquitto()
# Assign event callbacks
mqttc.on_message = on_message
mqttc.on_connect = on_connect
mqttc.on_publish = on_publish
mqttc.on_subscribe = on_subscribe

# Uncomment to enable debug messages
#mqttc.on_log = on_log

# Parse CLOUDMQTT_URL (or fallback to localhost)
url_str = os.environ.get('CLOUDMQTT_URL', 'mqtt://localhost:1883')
url = urlparse.urlparse(url_str)

# Connect
mqttc.username_pw_set(url.username, url.password)
mqttc.connect(url.hostname, url.port)

# Start subscribe, with QoS level 0
mqttc.subscribe("hello/world", 0)

# Publish a message
mqttc.publish("hello/world", "my message")

# Continue the network loop, exit when an error occurs
rc = 0
while rc == 0:
    rc = mqttc.loop()
print("rc: " + str(rc))

The full code can be seen at github.com/CloudMQTT/python-mqtt-example.

Using with Java

The by far best MQTT client for Java/JVM is Paho. Please email support@cloudmqtt.com if you need help to get started.

Dashboard

The CloudMQTT dashboard allows you to monitor your current connection and message traffic statistics.

The dashboard can be accessed via the CLI:

$ heroku addons:open cloudmqtt
Opening cloudmqtt for sharp-mountain-4005...

or by visiting the Heroku apps web interface and selecting the application in question. Select CloudMQTT from the Add-ons menu.

Migrating between plans

All plan migrations are completely transparent and instantaneous.

Use the heroku addons:upgrade command to migrate to a new plan.

$ heroku addons:upgrade cloudmqtt:newplan
-----> Upgrading cloudmqtt:newplan to sharp-mountain-4005... done, v18 ($49/mo)
       Your plan has been updated to: cloudmqtt:newplan

Removing the add-on

CloudMQTT can be removed via the CLI.

$ heroku addons:remove cloudmqtt
-----> Removing cloudmqtt from sharp-mountain-4005... done, v20 (free)

Support

All CloudMQTT support and runtime issues should be submitted on of the Heroku Support channels. Any non-support related issues or product feedback is welcome at support@cloudmqtt.com.