How to setup Mosquitto MQTT Broker using docker

These instructions will work on any Debian based OS including Ubuntu, RaspberryPi, WSL2 etc...
(For non-Debian distros, commands for installation need to be tweaked)

By default the config allows only to use local connections for security reasons but since authentication is enabled below, that's not the case.

1. Install docker

Latest instructions are here on docker website.
You can also use this script - install-docker.sh

2. Create base folder for mqtt configuration

mkdir mqtt5
cd mqtt5

# for storing mosquitto.conf and pwfile (for password)
mkdir config

3. Create Mosquitto config file - mosquitto.conf

nano config/mosquitto.conf

Basic configuration file content below including websocket config

allow_anonymous false
listener 1883
listener 9001
protocol websockets
persistence true
password_file /mosquitto/config/pwfile
persistence_file mosquitto.db
persistence_location /mosquitto/data/

4. Create Mosquitto password file - pwfile

touch config/pwfile

5. Create docker-compose file called 'docker-compose.yml'

version: "3.7"
services:
  # mqtt5 eclipse-mosquitto
  mqtt5:
    image: eclipse-mosquitto
    container_name: mqtt5
    ports:
      - "1883:1883" #default mqtt port
      - "9001:9001" #default mqtt port for websockets
    volumes:
      - ./config:/mosquitto/config:rw
      - ./data:/mosquitto/data:rw
      - ./log:/mosquitto/log:rw
    restart: unless-stopped

# volumes for mapping data,config and log
volumes:
  config:
  data:
  log:

networks:
  default:
    name: mqtt5-network

5.1 Public facing Mosquitto Websocket Server with Free SSL using Caddy Server

[!NOTE]
Setup and automate FREE valid SSL for Mosquitto Websocket (WSS), using Caddy Server with very minimal effort.

6. Create and run docker container for MQTT

# In case you don't have docker-compose you can install it
sudo apt install docker-compose

# Run the docker container for mqtt
sudo docker-compose -p mqtt5 up -d

Check if the container is up and working (note down container-id)

sudo docker ps

7. Create a user/password in the pwfile

# login interactively into the mqtt container
sudo docker exec -it <container-id> sh

# Create new password file and add user and it will prompt for password
mosquitto_passwd -c /mosquitto/config/pwfile user1

# Add additional users (remove the -c option) and it will prompt for password
mosquitto_passwd /mosquitto/config/pwfile user2

# delete user command format
mosquitto_passwd -D /mosquitto/config/pwfile <user-name-to-delete>

# type 'exit' to exit out of docker container prompt

Command line help for mosquitto_passwd command above

mosquitto_passwd is a tool for managing password files for mosquitto.

Usage: mosquitto_passwd [-H sha512 | -H sha512-pbkdf2] [-c | -D] passwordfile username
       mosquitto_passwd [-H sha512 | -H sha512-pbkdf2] [-c] -b passwordfile username password
       mosquitto_passwd -U passwordfile
 -b : run in batch mode to allow passing passwords on the command line.
 -c : create a new password file. This will overwrite existing files.
 -D : delete the username rather than adding/updating its password.
 -H : specify the hashing algorithm. Defaults to sha512-pbkdf2, which is recommended.
      Mosquitto 1.6 and earlier defaulted to sha512.
 -U : update a plain text password file to use hashed passwords

Then restart the container

sudo docker restart <container-id>

8. Time to test !!!

Install mosquitto client tools for testing

sudo apt install mosquitto-clients

Let us start Subscriber now - topic name => 'hello/topic'

# Without authentication
mosquitto_sub -v -t 'hello/topic'

# With authentication
mosquitto_sub -v -t 'hello/topic' -u user1 -P <password>

# Alternate way in url format
# Format => mqtt(s)://[username[:password]@]host[:port]/topic
mosquitto_sub -v -L mqtt://user1:abc123@localhost/test/topic

Let us start Publising to that topic

# Without authentication
mosquitto_pub -t 'hello/topic' -m 'hello MQTT'

# With authentication
mosquitto_pub -t 'hello/topic' -m 'hello MQTT' -u user1 -P <password>

# Alternate way in url format 
# Format => mqtt(s)://[username[:password]@]host[:port]/topic
mosquitto_pub -L mqtt://user1:abc123@localhost/test/topic -m 'hello MQTT'

You can find C/C++ code for mosquitto client

Check main.cpp for the mosquitto client code.

You can also install a nice MQTT Web Client

Read more about it here => https://mqttx.app/

sudo docker run -d --name mqttx-web -p 80:80 emqx/mqttx-web

Source/Reference for Mosquitto

Github => https://github.com/eclipse/mosquitto

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