That is MQTT ?
In short MQTT is a TCP / IP protocol lightweight messaging, the model is publication – subscriber requires a message broker which is responsible for directing recipients through a topic in common.
It is considered to Andrew James Stanford-Clark as the author of this protocol.
More information MQTT Wikipedia.
Official Website: mqtt.org
Application
I believe that this protocol is very practical and is currently implemented in IoT and M2M “machine-to-machine” applications, field application in this case would be sending monitoring and control data between servers, sensors and actuators.
Previous tutorials Recommended
Tutorial 1 : Install Lubuntu (Ubuntu)
Tutorial 2 : Installation node red platform
Tutorial 3 : Installation Node Red Dashboard
Tutorial 4: Installation Modbus TCP IP in Node Red
Architecture MQTT Protocol 
Broker Mosquitto MQTT
Eclipse mosquitto ™ It is open source, it is a message broker this intermediary MQTT allows the connection of devices.
Official Website: mosquitto.org
Installation of Mosquitto Broker MQTT in lubuntu (Ubuntu) Linux
MQTT to connect devices with Node-red I use mosquitto as Broker, this is an extra complement Node red in the next tutorial installation.
Enter the terminal lubuntu command as root.
sudo apt-add-repository ppa:mosquitto-dev/mosquitto-ppa
Update repositories linux
sudo apt-get update
Install broker mosquitto
sudo apt-get install mosquitto
Install development libraries
sudo apt-get install libmosquitto-dev
Installing client MQTT
sudo apt-get install mosquitto-clients
Check that mosquitto is running
sudo service mosquitto status
Ready to have fun …
Video Install Mosquitto MQTT Lubuntu Ubuntu Linux
Customer tests Mosquitto MQTT in lubuntu (Ubuntu) Linux
Subscriber
Our client is suscruibira the theme or topic “Sensor_MQTT” meaning that all published messages associated with this topic will be received.
mosquitto_sub -h localhost -t "Sensor_MQTT" -v
Publisher
Our client publish the message “Error Sensor” through the topic “Alert_MQTT”
mosquitto_pub -h localhost -t "Alert_MQTT" -m "Error_Sensor"
Ready to have fun …
Video Test Mosquitto MQTT in Lubuntu (Ubuntu) linux
ESP8266 & Public MQTT Broker mosquitto.org & Node-RED
References
Tutorial 1 : Install Lubuntu (Ubuntu)
Tutorial 2 : Installation node red platform
Tutorial 3: Installation Node Red Dashboard
Tutorial 4: Installation Modbus TCP IP in Node Red
node-red-dashboard
Nodered.org
github.com/node-red
Nodejs.org
Youtube Channel:
PDAControl