Add on_write_progress

src/main.cpp

@@ -29,8 +29,8 @@ void signal_handler(int sig) {
  */
 class EchoHandler : public ConnectionHandler {
 public:
-  void process_data(std::string_view data,
-                    std::unique_ptr<Connection> &conn_ptr) override {
+  void on_data_arrived(std::string_view data,
+                       std::unique_ptr<Connection> &conn_ptr) override {
     // Echo the received data back to the client
     conn_ptr->appendMessage(data);
   }