Quickly set up MQTT broker and clients
First post of 2025! I’ve been working on a few things but nothing that was worthy of a new post. Frustratingly, I’ve made slow progress with a challenging MQTT use case so I’m going to break this down into a few easy posts that I can refer to in future.
How to quickly deploy an MQTT broker
Start with Ubuntu
An MQTT broker can run on Windows, Linux, and of course can run inside K8s. I will document a quick K8s set up in a future post, but for now we’ll start with Ubuntu 22.04 LTS
Choose and install MQTT software
I’m going to choose Mosquitto because it’s popular. HiveMQ is also popular and perhaps I’ll do that in future too.
Mosquitto is available in the default package repositories, so you could run sudo apt install -y mosquitto and I will show an example of that below.
But after reading instructions from a few sites, you can also add the mosquitto-dev PPA to your repositories list to get more recent versions of mosquitto. So let’s do that.
At command line of Ubuntu VM:
sudo apt-get update
sudo apt-get install curl gnupg2 wget git apt-transport-https ca-certificates -y #install pre-reqs
sudo apt-add-repository ppa:mosquitto-dev/mosquitto-ppa -y #add repo
sudo apt-get update
sudo apt-get install mosquitto -y
sudo apt-get install mosquitto mosquitto-clients -y #run this if you also want to install client
#sudo systemctl status mosquitto #verify installation successful
#mosquitto -v #see version installedAlternatively, you could install from default repositories. As an example only, today (Jan 24, 2025) when I deploy a fresh Azure VM with Ubuntu 22.04, if I run the script above I will see that mosquitto version 2.0.20 is running. If I run the script below, it’s mosquitto version 2.0.11.
sudo apt update
sudo apt install -y mosquitto
#sudo systemctl status mosquitto #verify installation successful
#mosquitto -v #see version installedSo, I’m going to run with the first script, the one that installed 2.0.20
Configure mosquitto
You will notice there is now a file at /etc/mosquitto/mosquitto.conf, and there is a directory at /etc/mosquitto/conf.d/. You can edit the .conf file, and/or create your own .conf files in the directory to configure mosquitto.
First, let’s set a password. A file will be created at /etc/mosquitto/passwd where the username is mqttuser and the password is hashed in that file. We also need to set the correct ownership of that password file.
Second, let’s create a file at /etc/mosquitto/conf.d/default.conf. We’ll add a listener on port 1883 and tell mosquitto about the password file.
Lastly we will restart the mosquitto service.
sudo mosquitto_passwd -c /etc/mosquitto/passwd mqttuser
#enter password here
sudo chown mosquitto:mosquitto /etc/mosquitto/passwd
sudo bash -c 'cat > /etc/mosquitto/conf.d/default.conf <<EOF
listener 1883
password_file /etc/mosquitto/passwd
EOF
'
sudo systemctl restart mosquittoTest connectivity
Locally on the same VM
For this you must have the mqtt clients installed, so I have just run sudo apt-get install mosquitto-clients -y on my Ubuntu VM and will test locally on the machine.
Create a client to subscribe:
mosquitto_sub -u mqttuser -P password -v -t "hello/topic"Now, create a client to publish:
mosquitto_pub -u mqttuser -P password -t 'hello/topic' -m 'hello MQTT'Over the network using a different MQTT client software
In this case I have set up a MQTT client on another VM, using the MQTT CLI from HiveMQ. I’ll include the commands to install this MQTT client cli purely for the sake of trying something different.
Notice that I include -h x.x.x.x in my command - that’s the public IP address of the temporary MQTT broker I have set up.
#install mqtt cli
wget https://github.com/hivemq/mqtt-cli/releases/download/v4.35.0/mqtt-cli-4.35.0.deb
sudo apt install ./mqtt-cli-4.35.0.deb
mqtt sub -t hello/topic -h x.x.x.x -u mqttuser -pw passwordThen, in another window on the same box:
mqtt pub -t hello/topic -m '12345' -h x.x.x.x -u mqttuser -pw password