##Enabling MQTT MQTT is a "lightweight" messaging protocol, which enables the publishing of data from emoncms, as well as subscribing to data from other connected devices. ###Preparation
Before following this guide, it is essential that emoncms was initially installed by following the Raspberry Pi installation guide or you have used git to install a working version of emoncms on your Raspberry Pi, as well as a MQTT message broker such as mosquitto installed and running.
Update emoncms to current version
cd /var/www/emoncms && git pull
Create a symlink to run phpmqtt_input as a daemon and set permissions
cd /etc/init.d && sudo ln -s /var/www/emoncms/scripts/mqtt_input
sudo chown root:root /var/www/emoncms/scripts/mqtt_input
sudo chmod 755 /var/www/emoncms/scripts/mqtt_input
sudo update-rc.d mqtt_input defaults
###Enable MQTT in emoncms
nano /var/www/emoncms/settings.php
In the section MQTT, change $mqtt_enabled from false to true, and also change the $mqtt_server IP address to that of your mqtt
server.
Save & exit, then reboot
sudo reboot
###Node format
####emoncms as a publisher
Data from within emoncms can be published by adding the Publish to MQTT input process to one or more of the node inputs.
In the process 'Text' box add the topic, for example; emoncms/solar
####emoncms as a subscriber
Unlike the above, the subscriber topic is hardcoded within emoncms, and takes the format rx/* - where * is the emoncms node number. For example, if data is published to topic rx/20 then emoncms will subscribe to that data, creating and updating node 20 in your inputs page