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Pure Ruby gem that implements the MQTT protocol, a lightweight protocol for publish/subscribe messaging.
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 Project Readme

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ruby-mqtt

Pure Ruby gem that implements the MQTT protocol, a lightweight protocol for publish/subscribe messaging.

Also includes a class for parsing and generating MQTT-SN packets.

Table of Contents

  • Installation
  • Quick Start
  • Library Overview
  • Resources
  • License
  • Contact

Installation

You may get the latest stable version from Rubygems:

$ gem install mqtt-ccutrer

Quick Start

require 'mqtt'

# Publish example
MQTT::Client.connect('test.mosquitto.org') do |c|
  c.publish('test', 'message')
end

# Subscribe example
MQTT::Client.connect('test.mosquitto.org') do |c|
  # If you pass a block to the get method, then it will loop
  c.subscribe('test')
  c.get do |packet|
    puts "#{packet.topic}: #{packet.payload}"
  end
end

Library Overview

Connecting

A new client connection can be created by passing either a MQTT URI, a host and port or by passing a hash of attributes.

client = MQTT::Client.connect('mqtt://myserver.example.com')
client = MQTT::Client.connect('mqtts://user:pass@myserver.example.com')
client = MQTT::Client.connect('myserver.example.com')
client = MQTT::Client.connect('myserver.example.com', 18830)
client = MQTT::Client.connect(host: 'myserver.example.com', port: 1883 ... )

TLS/SSL is not enabled by default, to enabled it, pass ssl: true:

client = MQTT::Client.connect(
  host: 'test.mosquitto.org',
  port: 8883,
  ssl: true
)

Alternatively you can create a new Client object and then configure it by setting attributes. This example shows setting up client certificate based authentication:

client = MQTT::Client.new
client.host = 'myserver.example.com'
client.ssl = true
client.cert_file = path_to('client.pem')
client.key_file  = path_to('client.key')
client.ca_file   = path_to('root-ca.pem')
client.connect

The connection can either be made without the use of a block:

client = MQTT::Client.connect('test.mosquitto.org')
# perform operations
client.disconnect

Or, if using a block, with an implicit disconnection at the end of the block.

MQTT::Client.connect('test.mosquitto.org') do |client|
  # perform operations
end

For more information, see the list of attributes for the MQTT::Client class and the MQTT::Client.connect method.

Publishing

To send a message to a topic, use the publish method:

client.publish(topic, payload, retain: false, qos: 0)

The method will return once the message has been sent to the MQTT server for QoS 0, or once an Ack has been received from the server for QoS 1.

For more information see the MQTT::Client#publish method.

Subscribing

You can send a subscription request to the MQTT server using the subscribe method. One or more Topic Filters may be passed in:

client.subscribe( 'topic1' )
client.subscribe( 'topic1', 'topic2' )
client.subscribe( 'foo/#' )

For more information see the MQTT::Client#subscribe method.

Receiving Messages

To receive a message, use the get method. This method will block until a message is available. You can access details about the packet such as if it was retained, the topic it was sent to, and the payload.

packet = client.get
packet.retained?
packet.topic
packet.payload

Alternatively, you can give the get method a block, which will be called for every message received and loop forever:

client.get do |packet|
  # Block is executed for every message received
end

For more information see the MQTT::Client#get method.

Parsing and serialising of packets

The parsing and serialising of MQTT and MQTT-SN packets is a separate lower-level API. You can use it to build your own clients and servers, without using any of the rest of the code in this gem.

# Parse a string containing a binary packet into an object
packet_obj = MQTT::Packet.parse(binary_packet)
    
# Write a PUBACK packet to an IO handle
ios << MQTT::Packet::Puback(id: 20)
    
# Write an MQTT-SN Publish packet with QoS -1 to a UDP socket
socket = UDPSocket.new
socket.connect('localhost', MQTT::SN::DEFAULT_PORT)
socket << MQTT::SN::Packet::Publish.new(
  topic_id: 'TT',
  topic_id_type: :short,
  data: "The time is: #{Time.now}",
  qos: -1
)
socket.close

Limitations

  • QoS 2 is not currently supported by client
  • Pending publishes are only persisted as long as a reconnect occurs within the configured timeout

Resources

License

The mqtt ruby gem is licensed under the terms of the MIT license. See the file LICENSE for details.