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

Example receiving latest message from a topic:
```cpp
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:
```cpp
void foo(std::string Message){
    //channel, payload
    client.publishMessage("kobuki/example", Message);
}
```