Mosquitto

Introduction

• MQTT is a very lightweight messaging protocol
• Specifically designed for machine-to-machine telemetry
• The MQTT protocol is based on a TCP connection.
• IBM Watson uses MQTT to allow it to communicate with devices.

Pros

• Lightweight and efficient—which means it’s optimal for small bandwidth environments such as microcontrollers
• Bi-directional communications
• Messages are encrypted using TLS
• Offers support for unreliable networks using persistent sessions

Cons

• Doesn’t support video streaming
• Messages are transmitted asynchronously
• Can experience issues with latency and speed.

Install server

sudo apt-get install mosquitto

Install client

sudo apt-get install mosquitto mosquitto-clients

Subscribe a topic

mosquitto_sub -t "test_topic"

Publish on topic

mosquitto_pub -t "test_topic" -m "HELLO WORLD!"

Testing the communication

Producer:

mosquitto_pub -t "test_topic" -m "HELLO WORLD!"
for i in {1..10}; do mosquitto_pub -t "test_topic" -m "I=$i"; done

Consumer:

mosquitto_sub -t "test_topic"
HELLO WORLD!
I=1
I=2
I=3
I=4
I=5
I=6
I=7
I=8
I=9
I=10

C++ and C library

sudo apt install libmosquitto-dev
or 
sudo apt install libpaho-mqtt-dev

References

• 8 Most Popular Instant Messaging & Chat Protocols
• Everything About MQTT Protocol — Message Queue Telemetry Transport
• How to Install and Secure the Mosquitto MQTT Messaging Broker on Ubuntu 16.04
• How to Install and Secure the Mosquitto MQTT Messaging Broker on Debian 8
• Mosquitto C++ sample code to publish message
• Eclipse Paho MQTT C++ Client Library
• https://github.com/eclipse/paho.mqtt.cpp/tree/master/src/samples
• libmosquittopp - sample client hangs on loop_stop() method
• https://medium.com/tht-things-hackers-team/instalar-mqtt-broker-no-linux-debian-ubuntu-f8861da70ef6
• https://android.developreference.com/article/16161720/libmosquittopp+-+sample+client+hangs+on+loop_stop()+method