Mosquitto Broker

We will start with the mosquitto container, which acts as a message broker that implements the MQTT protocol. It allows any device connected to the same network to publish or subscribe to topics. This allows for establishing communication between different devices.

In this example, it is used slightly differently. Instead of different devices communicating, two different containers will use MQTT to establish communication between them.

Open a new terminal on your host machine and find the container folder used previously.

cd containers/

While in the containers folder, use git to download mosquitto from the extra-containers repo:

git remote add fio https://github.com/foundriesio/extra-containers.git
git remote update
git checkout remotes/fio/tutorials -- mosquitto

The mosquitto app with docker-compose.yml should now be inside your containers folder:

tree -L 2 .

.
├── mosquitto
│   └── docker-compose.yml
├── README.md
└── shellhttpd
    ├── docker-build.conf
    ├── docker-compose.yml
    ├── Dockerfile
    ├── httpd.sh
    └── shellhttpd.conf

Check the content of mosquitto/docker-compose.yml:

cat mosquitto/docker-compose.yml

# mosquitto/docker-compose.yml
version: '3.2'

services:
  mosquitto:
    image: eclipse-mosquitto:1.6.12
    restart: unless-stopped
    ports:
      - 1883:1883

The mosquitto/docker-compose.yml file has all the configuration for the mosquitto app:

  • version: Denotes what Docker Compose version it is using.
  • services: Defines the containers it will create.
  • mosquitto: Name of the first service.
  • image: Specifies the pre-built Docker container image, eclipse-mosquitto version 1.6.12 from hub.docker.com.
  • restart: Specifies unless-stopped, which means that the Docker container will not restart if the container is stopped—manually or otherwise—even after the Docker daemon restarts.
  • port: Map the container’s ports to the host machine