...

net/adc_netserver.h

@@ -353,13 +353,16 @@ protected:
                 _isListening<SessionT>[this][id] = true;
                 doAccept<SessionT>(acceptor, std::move(id), std::move(sess_ctx));
             } else {
-                errorMessage(SessionT::netservice_t::formatError(ec));
+                std::string str{"Cannot start accepting connection: "};
+                SessionT::netservice_t::formatError(ec, str);
+                errorMessage(str);
+
                 _isListening<SessionT>[this][id] = false;
             }
         });
     }
 
-    virtual void errorMessage(const std::string&) = 0;
+    virtual void errorMessage(const std::string&) {};
 };