These are my notes from installing the Mosquitto MQTT broker on my Mac computer. And then publishing sensor data with an ESP32 Devboard and subscribing to the data with a Processing sketch.

installing Mosquitto on Mac

>> https://subscription.packtpub.com/book/application-development/9781787287815/1/ch01lvl1sec12/installing-a-mosquitto-broker-on-macos

open terminal
Install mosquitto: brew install mosquitto

CHANGE SOME SETTINGS
before running mosquitto we need to change some settings in the mosquitto config file so that it does not require ID and password:
Open the config file via terminal: pico /usr/local/etc/mosquitto/mosquitto.conf
in the config file search (ctrl-w) for “allow_anonymous”
should get you to this line: #allow_anonymous false
remove the “#” and change it to be: allow_anonymous true
add this line above: listener 1883
so that you have:
listener 1883
allow_anonymous true
close pico editor: ctrl + x
save: yes

RUN MOSQUITTO
to open/start mosquitto you can use the following lines in the terminal (the file paths will be different for you!): /usr/local/sbin/mosquitto -c /usr/local/etc/mosquitto/mosquitto.conf
to stop mosquitto: ctrl + c

ERROR: address already in use
if you get this error when trying to start mosquitto you can force quit mosquitto from the activity monitor.


try again and hopefully you see this:

publishing data with ESP32

CONNECTING
to connect to the broker you need to know your computer’s IP address, which is also your broker’s IP address as it is running on your computer. you find it in the network advanced settings:

ARDUINO CODE

subscribing with Processing

PROCESSING CODE