MQTTBroker

Install MQTT broker and client on the VPS server

# Install Mosquitto MQTT broker
sudo apt-get --yes install mosquitto mosquitto-clients
sudo systemctl start mosquitto
systemctl status mosquitto
mosquitto -h # mosquitto version 1.5.7; MQTT v3.1.1

Install MQTT client on Raspberry PI Zero

sudo apt-get --yes install mosquitto-clients

Clone Practical-Python-Programming-for-IoT repository

git clone https://github.com/PacktPublishing/Practical-Python-Programming-for-IoT.git pyiot

Configure mqtt broker. You need to change http_dir path. The content of file mosquitto_pyiot.conf is as follows. You may need to allow port 1883 and 8083 to pass through your sever firewall. If your server is using ufw, the command below can be used.

sudo ufw allow 1883
sudo ufw allow 8083

For an unknown reason, mosquitto did not work with my user directory, so I need to move mosquitto_www into a new directory.

sudo mv /home/tuyenld/mqtt-python/pyiot/chapter04/mosquitto_www /etc/mosquitto/conf.d/mosquitto_www

Add username/password configuration.

cd /etc/mosquitto/conf.d/
mosquitto_passwd -c pass piZero # password is pihat :)

# sudo vi /etc/mosquitto/conf.d/mosquitto_pyiot.conf
persistence true

# MQTT Protocol
listener 1883 0.0.0.0
# password file created above
password_file /etc/mosquitto/conf.d/pass
protocol mqtt

# Web Sockets Protocol
listener 8083 0.0.0.0
protocol websockets
http_dir /etc/mosquitto/conf.d/mosquitto_www

Restart mosquitto broker and test connection.

sudo systemctl restart mosquitto
# make sure that the new configuration is applied
systemctl status mosquitto

# Test connention
wget http://localhost:8083
Remember that MQTT uses ports 1883 and 8883 (for SSL).

Clear all retained message

sudo systemctl stop mosquitto.service
sudo rm /var/lib/mosquitto/mosquitto.db
sudo systemctl start mosquitto.service
sudo systemctl status mosquitto.service

Test

# [subscriber] Terminal1 of Raspberry Pi 
# Using username and password created
mosquitto_sub -u piZero -P pihat -v -h 104.248.243.162 -t 'hat'

# [publisher] Terminal2 of VPS server (MQTT broker)
# the message 'hello' should be received at Terminal1
mosquitto_pub -u piZero -P pihat -h 104.248.243.162 -t 'hat' -m 'hello'

Debug

sudo cat /var/log/mosquitto/mosquitto.log

systemctl status mosquitto

# Or alternatively, execute the following command to start Mosquitto manually
# which will display any startup or configurations errors in the Terminal
sudo mosquitto -v -c /etc/mosquitto/mosquitto.conf

# clear log file
sudo truncate -s 0  /var/log/mosquitto/mosquitto.log

cpp

Install on Raspberry Pi

# https://mosquitto.org/blog/2013/01/mosquitto-debian-repository/
sudo apt-get install mosquitto

# https://jpinjpblog.wordpress.com/2017/12/18/installing-mqtt-for-c-on-raspberry-pi/
sudo apt-get install libmosquitto-dev libmosquittopp-dev libssl-dev

sudo vi /etc/mosquitto/conf.d/websocket.conf
listener 1883
listener 1884
protocol websockets

sudo service mosquitto restart

# As long as you make your code with the following flags.
# -l mosquittopp

Libs

• mosquittopp.h
• mosquitto.h

Python programming

Raspberry Pi configuration

sudo apt install python3-pip
sudo apt-get install python3-venv
python3 -m venv hat-env
source hat-env/bin/activate

pip install paho-mqtt

• -q2 QOS 2: The message will be delivered exactly once.
• -c --disable-clean-session: keep messages while I am offline.

# subscriber
mosquitto_sub -c -q2 -u piZero -P pihat -v -h 104.248.243.162 -t 'hat'

# publisher
mosquitto_pub -u piZero -P pihat -h 104.248.243.162 -t 'hat' -m 'hello'


# Durable connection
# qos is needed for both sub and pub
# -c : disable clean session/enable persistent client mode
mosquitto_pub -q 2 -h test.mosquitto.org -t "example/temperature" -m 'hello'
mosquitto_sub -q 2 -c -i durable_id -h test.mosquitto.org -t "example/temperature"

The MQTT client is single threaded, it will only receive and process one message at a time