- MQTT is open, simple and low overhead communication protocol for sending messages between many clients which are connected to the central MQTT broker.
- Every message contains two parts - topic and payload.
- Topic describes content of the message.
- Topic name contains "directory" structure - each level is divided with symbol
- Topic can be
- MQTT server is called the broker and clients can publish messages and subscribe to different topics.
- The task of MQTT broker is to deliver messages from publishers to the subscribers.
- You can use the
+symbol to subscribe to all topics in the current topic (
#symbol to subscribe to all sub-topics (
#can be used only at the end of the topic name.
Mosquitto MQTT broker
BigClown is using open-source Mosquitto MQTT broker. All messages are routed through MQTT broker. This allows further expansion of BigClown system.
When you connect the Core Module or USB Dongle with connected remote node, you can display all incoming messages using
mosquitto-cli package by typing:
pi@hub:~ $ mosquitto_sub -t "#" -v node/836d19821664/thermometer/0:1/temperature 24.69 node/836d19821664/thermometer/0:1/temperature 24.94 node/836d19821664/push-button/-/event-count 5
GUI tool for MQTT messages
For debugging the communication you can use graphical tool Eclipse Paho mqtt-spy.
More information about Paho https://github.com/eclipse/paho.mqtt-spy/wiki
After installation you have to set IP adress of the MQTT broker. For example
hub.local or IP adress of your Raspberry Pi