Book Image

Hands-On MQTT Programming with Python

By : Gaston C. Hillar
Book Image

Hands-On MQTT Programming with Python

By: Gaston C. Hillar

Overview of this book

<p>MQTT is a lightweight messaging protocol for small sensors and mobile devices. This book explores the features of the latest versions of MQTT for IoT and M2M communications, how to use them with Python 3, and allow you to interact with sensors and actuators using Python.</p> <p>The book begins with the specific vocabulary of MQTT and its working modes, followed by installing a Mosquitto MQTT broker. You will use different utilities and diagrams to understand the most important concepts related to MQTT. You will learn to make all the necessary configuration to work with digital certificates for encrypting all data sent between the MQTT clients and the server. You will also work with the different Quality of Service levels and later analyze and compare their overheads.</p> <p>You will write Python 3.x code to control a vehicle with MQTT messages delivered through encrypted connections (TLS 1.2), and learn how leverage your knowledge of the MQTT protocol to build a solution based on requirements. Towards the end, you will write Python code to use the PubNub cloud-based real-time MQTT provider to monitor a surfing competition.</p> <p>In the end, you will have a solution that was built from scratch by analyzing the requirements and then write Python code that will run on water-proof IoT boards connected to multiple sensors in surfboards.</p>
Table of Contents (9 chapters)

Installing a Mosquitto server on Linux

Now, we will learn the necessary steps to install a Mosquitto server on the most popular operating systems: Linux, macOS, and Windows.

It is extremely important to work with the latest available Mosquitto versions to make sure that many security vulnerabilities discovered in previous versions are addressed. For example, Mosquitto 1.4.15 addressed two important security vulnerabilities that affected versions 1.0 to 1.4.14 inclusive.

First, we will start with Linux; specifically, we will work with Ubuntu Linux. If you want to work with a different Linux distribution, you can find details about the installation procedure in the Mosquitto downloads section: http://mosquitto.org/download.

Follow these steps to install a Mosquitto server on Ubuntu Linux; take into account that you will require root privileges:

  1. Open a Terminal window or use a secure shell to access Ubuntu and run the following command to add the Mosquitto repository:
      sudo apt-add-repository ppa:mosquitto-dev/mosquitto-ppa

You will see an output similar to the next lines (the temporary filenames will be different):

      gpg: keyring `/tmp/tmpi5yrsz7i/secring.gpg' created
gpg: keyring `/tmp/tmpi5yrsz7i/pubring.gpg' created
gpg: requesting key 262C4500 from hkp server keyserver.ubuntu.com
gpg: /tmp/tmpi5yrsz7i/trustdb.gpg: trustdb created
gpg: key 262C4500: public key "Launchpad mosquitto" imported
gpg: Total number processed: 1
gpg: imported: 1 (RSA: 1)
OK
  1. Run the following command to update the packages with the recently added Mosquitto repository:
      sudo apt-get update

You will see an output similar to the next lines. Note that the next lines show the output of an Ubuntu server running as a Windows Azure virtual machine, and therefore the output will be similar:

      Hit:1 http://azure.archive.ubuntu.com/ubuntu xenial InRelease
Get:2 http://azure.archive.ubuntu.com/ubuntu xenial-updates
InRelease [102 kB]
Get:3 http://azure.archive.ubuntu.com/ubuntu xenial-backports
InRelease [102 kB]

...

Get:32 http://security.ubuntu.com/ubuntu xenial-security/universe
Translation-en [121 kB]
Get:33 http://security.ubuntu.com/ubuntu xenial-
security/multiverse amd64 Packages [3,208 B]
Fetched 12.8 MB in 2s (4,809 kB/s)
Reading package lists... Done
  1. Now, run the following command to install the package for the Mosquitto server:
      sudo apt-get install mosquitto

You will see an output similar to the next lines.

  1. Enter Y and press Enter to answer the question and complete the installation process:
      Building dependency tree
Reading state information... Done
The following additional packages will be installed:
libev4 libuv1 libwebsockets7
The following NEW packages will be installed:
libev4 libuv1 libwebsockets7 mosquitto
0 upgraded, 4 newly installed, 0 to remove and 29 not upgraded.
Need to get 280 kB of archives.
After this operation, 724 kB of additional disk space will be
used.
Do you want to continue? [Y/n] Y
  1. The last lines should include a line that says Setting up mosquitto followed by the version number, as shown in the following lines:
      Setting up libuv1:amd64 (1.8.0-1) ...
Setting up libev4 (1:4.22-1) ...
Setting up libwebsockets7:amd64 (1.7.1-1) ...
Setting up mosquitto (1.4.15-0mosquitto1~xenial1) ...
Processing triggers for libc-bin (2.23-0ubuntu10) ...
Processing triggers for systemd (229-4ubuntu21.1) ...
Processing triggers for ureadahead (0.100.0-19) ...
  1. Now, run the following command to install the Mosquitto client packages that will allow us to run commands to publish messages to topics and subscribe to topic filters:
      sudo apt-get install mosquitto-clients

You will see an output similar to the next lines.

  1. Enter Y and press Enter to answer the question and complete the installation process:
      Reading package lists... Done
Building dependency tree
Reading state information... Done
The following additional packages will be installed:
libc-ares2 libmosquitto1
The following NEW packages will be installed:
libc-ares2 libmosquitto1 mosquitto-clients
0 upgraded, 3 newly installed, 0 to remove and 29 not upgraded.
Need to get 144 kB of archives.
After this operation, 336 kB of additional disk space will be
used.

Do you want to continue? [Y/n] Y

The last lines should include a line that says Setting up mosquitto-clients followed by the version number, as shown in the following lines:

      Setting up libmosquitto1:amd64 (1.4.15-0mosquitto1~xenial1) ...
Setting up mosquitto-clients (1.4.15-0mosquitto1~xenial1) ...
Processing triggers for libc-bin (2.23-0ubuntu10) ...
  1. Finally, run the following command to check the status for the mosquitto service that was recently installed:
      sudo service mosquitto status

The first lines of the output should be similar to the following lines with an active (running) status displayed. The details after CGroup indicate the command line that started the service. The -c option followed by /etc/mosquitto/mosquitto.conf specifies that Mosquitto is using this configuration file:

mosquitto.service - LSB: mosquitto MQTT v3.1 message broker
Loaded: loaded (/etc/init.d/mosquitto; bad; vendor preset: enabled)
Active: active (running) since Sun 2018-03-18 19:58:15 UTC; 3min 8s ago
Docs: man:systemd-sysv-generator(8)
CGroup: /system.slice/mosquitto.service
└─15126 /usr/sbin/mosquitto -c /etc/mosquitto/mosquitto.conf

You can also run the following command to check whether the Mosquitto MQTT server is listening at the default port, 1883:

netstat -an | grep 1883

The following lines show the results of the previous command that indicate the Mosquitto MQTT server has opened an IPv4 and an IPv6 listen socket on port 1883:

tcp 0 0 0.0.0.0:1883 0.0.0.0:* LISTEN

tcp6 0 0 :::1883 :::* LISTEN