J2S1-Kobuki/docs/code/Mqtt.md

MQTT

What is MQTT?

MQTT is a lightweight messaging protocol made for IOT devices. It allows efficient communication between IoT devices, servers, and applications by allowing them to publish and subscribe to messages.

How to connect

To connect to a MQTT server you need to create a instance of the class.

Example:

// server adress, Client ID, Client Username, Client Password
MqttClient client("ws://145.92.224.21/ws/", "KobukiRPI", "rpi", "rpiwachtwoordofzo"); // create a client object

Later in the setup function you need to call client.connect(); to connect to the mqtt server.

    client.connect();

When you've connected and the instance is initiated you can subscribe to topics or send messages to topics.

Subscribing and receiving messages

Example subscribing to a topic:

void setup(){
    client.subscribe("home/commands");
}

Example receiving latest message from a topic:

std::string foo(){
    std::string latestMqttMessage = "";
    latestMqttMessage = client.getLastMessage();
    return latestMqttMessage;
}

If you want to subscribe to mulitple topics you need to initiate multiple instances of the mqtt class.

Publishing messages

Example publishing a message:

void foo(std::string Message){
    //channel, payload
    client.publishMessage("kobuki/example", Message);
}