Added Class implementation example

examples/BasicClassExample/BasicClassExample.ino

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+/*
+* Basic example of using the library arduino-mqtt by 256dpi as a class
+* 
+* Edit platformio.ini to match your board. By default it's set to be 
+* used with an Adafruit Feather Esp32-S3 with no psram.
+* 
+* Edit the server settings in Connectivity.h to the Broker/server you
+* want to use. There's more details in the README.md file.
+*/
+
+#include <Arduino.h>
+#include "Connectivity.h"
+
+Connectivity connection;
+
+void setup() {
+  Serial.begin(115200);
+  delay(3000); // Give Serial a little time to connect
+  connection.begin();
+}
+
+void loop() {
+  connection.loop(); // Stay connected
+}

examples/BasicClassExample/Connectivity.cpp

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+#include "Connectivity.h"
+
+Connectivity::Connectivity(){
+
+}
+
+void Connectivity::begin(){
+    // Setup connection
+    mqttClientID = WiFi.macAddress();
+    mqttClient.ref = this;
+    mqttClient.begin(mqttServer.c_str(), mqttPort, networkClient);
+    reconnect();
+}
+
+void Connectivity::loop(){
+    mqttClient.loop();
+
+    // Stay connected
+    if (!mqttClient.connected()) {
+        reconnect();
+    }
+
+    // Send ping now and then
+    if (millis() > nextStatusMessage) {
+        nextStatusMessage = millis()+10000;
+        sendStatus();
+    }
+}
+
+bool Connectivity::reconnect(){
+    if( WiFi.status() != WL_CONNECTED )
+    {
+        WiFi.mode(WIFI_STA);
+        WiFi.begin(ssid.c_str(), password.c_str());
+        while (WiFi.status() != WL_CONNECTED){
+            Serial.print(".");
+            delay(500);
+        }
+        log_i("Connected to %s", WiFi.SSID().c_str());
+    }
+
+    // Connect to MQTT
+    mqttClient.onMessageAdvanced( messageReceived );
+    bool ret = mqttClient.connect(mqttClientID.c_str(), mqttUsername.c_str(), mqttPassword.c_str());
+    if( ret )
+    {
+        String topic = String("/device/") + mqttClientID+"/update";
+        Serial.print("Subscribing to ");
+        Serial.println(topic.c_str());
+        mqttClient.subscribe( topic.c_str() );
+
+        Serial.print("Open a tool like MQTT Explorer and send a message to ");
+        Serial.println(topic.c_str());
+
+        Serial.println("You should then see the message on the Serial Monitor (if you open it)");
+
+        sendStatus();
+    }
+    return ret;
+}
+
+void Connectivity::sendStatus(){
+    String topic = String("/device/") + mqttClientID+"/status";
+    String payload = "{\"status\": \"online\"}";
+    mqttClient.publish(topic.c_str(), payload.c_str());
+}
+
+// See https://github.com/256dpi/arduino-mqtt/pull/220 for details
+ MQTTClientCallbackAdvancedFunction Connectivity::messageReceived(MQTTClient *client, char topic[], char bytes[], int length)
+ {
+    String cTopic = topic;
+    String cPayload = bytes;
+    Serial.print("messageReceived on topic: ");
+    Serial.print(cTopic);
+    Serial.print(" payload: ");
+    Serial.println(cPayload);
+
+    auto parent = (Connectivity *)client->ref;
+    if( parent != nullptr )
+    {
+        Serial.print("RefTest: ");
+        Serial.println(parent->mqttServer);
+    }
+    return NULL;
+}

examples/BasicClassExample/Connectivity.h

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+
+#ifndef MQTT_CONNECTIVITY_h
+#define MQTT_CONNECTIVITY_h
+
+#include <WiFi.h>
+#include <MQTT.h>
+
+class Connectivity {
+    public:
+        Connectivity();
+        void begin();
+        void loop();
+        void sendStatus();
+        bool reconnect();
+        static MQTTClientCallbackAdvancedFunction messageReceived(MQTTClient *client, char topic[], char bytes[], int length);
+    private:
+        // Edit your server settings here
+        WiFiClient networkClient;
+        String ssid =     "EnterYourSsidHere"; 
+        String password = "EnterYourWifiPasswordHere";
+
+        MQTTClient mqttClient;
+        String mqttServer = "test.mosquitto.org";
+        String mqttUsername = "";
+        String mqttPassword = "";
+        String mqttClientID = "undefined";
+        int mqttPort = 1883;
+
+        unsigned long nextStatusMessage = 0;
+};
+
+#endif // MQTT_CONNECTIVITY_h