...

net/adc_net_concepts.h

@@ -47,6 +47,20 @@ using adc_common_duration_t = adc_duration_common_type_t<std::chrono::nanosecond
                                                          std::chrono::months,
                                                          std::chrono::years>;
 
+// concepts for asynchronous opereration callback callable first argument type (asynchronous operation error)
+//      1) the type must be convertible to boolean and
+//         a) true - asynchronous operation completed without errors
+//         b) false - an error occured
+template <typename ERRT>
+concept adc_async_callback_err_t = std::convertible_to<std::remove_cvref_t<ERRT>, bool>;
+
+// concepts for asynchronous opereration callback callable
+//      1) the type must be a callable with at least 1 input argument
+//      2) the first argument type must satisfy the concept adc_async_callback_err_t
+template <typename T>
+concept adc_async_callback_t = traits::adc_is_callable<T> && traits::adc_func_traits<T>::arity &&
+                               adc_async_callback_err_t<traits::adc_func_arg1_t<T>>;
+
 /*
     struct NetService {
         typedef ImplementationDependentT netservice_ident_t;

net/adc_netserver.h

@@ -130,32 +130,10 @@ protected:
         }
     }
 
-    virtual void daemonizePrepare()
-    {
-        //
-        _impl.daemonizePrepare();
-    };
+    virtual void daemonizePrepare() = 0;
 
-    virtual void daemonizeFinalize()
-    {
-        //
-        _impl.daemonizeFinalize();
-    };
+    virtual void daemonizeFinalize() = 0;
 };
 
 
-namespace traits
-{
-
-// network server concept
-template <typename T>
-concept adc_netserver_c = requires {
-    typename T::server_impl_t;
-    std::derived_from<T, AdcNetServer<typename T::server_impl_t>>;
-};
-
-}  // namespace traits
-
-
-
 }  // namespace adc

net/asio/adc_netservice_asio.h

@@ -380,6 +380,7 @@ public:
                     if (start) {
                         start = false;
                         if (_receiveQueue.size()) {  // return message from queue
+                            timer->cancel();
                             msg = _receiveQueue.front();
                             _receiveQueue.pop();
                             if constexpr (std::is_same_v<msg_t, RMSGT>) {