Integrate Paho MQTT C library into project. Updated CMakeLists.txt to find PahoMqttC package and added fallback for manual linking. Refactored mqtt.hpp and mqtt.cpp to utilize Paho MQTT C API, replacing previous async client implementation. Added Windows setup guide for MQTT library installation.

include/mqtt.hpp

@@ -9,7 +9,7 @@
 #include <mutex>
 #include <condition_variable>
 #include <nlohmann/json.hpp>
-#include <mqtt/async_client.h>
+#include <MQTTClient.h>  // Paho MQTT C library
 
 namespace custom {
 
@@ -39,34 +39,22 @@ public:
     void stopMessageProcessor();
 
 private:
-    class Callback : public virtual mqtt::callback,
-                     public virtual mqtt::iaction_listener {
-    public:
-        Callback(MqttClient* client) : client_(client) {}
-
-        void connected(const std::string& cause) override;
-        void connection_lost(const std::string& cause) override;
-        void message_arrived(mqtt::const_message_ptr msg) override;
-        void delivery_complete(mqtt::delivery_token_ptr token) override;
-
-        void on_failure(const mqtt::token& tok) override;
-        void on_success(const mqtt::token& tok) override;
-
-    private:
-        MqttClient* client_;
-    };
-
     struct QueuedMessage {
         std::string topic;
         std::string payload;
     };
 
+    // C callback functions (static)
+    static int messageArrivedCallback(void* context, char* topicName, int topicLen, MQTTClient_message* message);
+    static void connectionLostCallback(void* context, char* cause);
+    static void deliveryCompleteCallback(void* context, MQTTClient_deliveryToken dt);
+
     void processMessageQueue();
     void handleConnectionLost();
     void handleConnectionEstablished();
+    void reconnectWorker();
 
-    std::unique_ptr<mqtt::async_client> client_;
-    std::unique_ptr<Callback> callback_;
+    MQTTClient client_;
     
     MessageCallback messageCallback_;
     ConnectionCallback connectionCallback_;
@@ -82,8 +70,7 @@ private:
     std::atomic<bool> processorRunning_;
     
     // Connection parameters
-    std::string broker_;
-    int port_;
+    std::string serverURI_;
     std::string clientId_;
     std::string username_;
     std::string password_;
@@ -92,6 +79,9 @@ private:
     std::thread reconnectThread_;
     std::atomic<bool> shouldReconnect_;
     int reconnectDelay_ = 5; // seconds
+    
+    // Connection options
+    MQTTClient_connectOptions connOpts_;
 };
 
 } // namespace custom