More comments in demos to help you understand passive receiving and message handling more.

examples/echo_client/echo_client.cpp

@@ -123,6 +123,8 @@ protected:
 		//except we can bear message disordering.
 
 		return 1;
+		//if we indeed handled some messages, do return 1
+		//if we handled nothing, return 1 is also okey but will very slightly impact performance (if msg_can is not empty), return 0 is suggested
 	}
 #endif
 #ifdef ASCS_DISPATCH_BATCH_MSG
@@ -136,6 +138,8 @@ protected:
 
 		ascs::do_something_to_all(tmp_can, [this](out_msg_type& msg) {this->handle_msg(msg);});
 		return 1;
+		//if we indeed handled some messages, do return 1
+		//if we handled nothing, return 1 is also okey but will very slightly impact performance, return 0 is suggested
 	}
 #else
 	virtual bool on_msg_handle(out_msg_type& msg) {handle_msg(msg); return true;}

examples/echo_server/echo_server.cpp

@@ -117,6 +117,8 @@ protected:
 		msg_can.clear();
 
 		return 1;
+		//if we indeed handled some messages, do return 1
+		//if we handled nothing, return 1 is also okey but will very slightly impact performance (if msg_can is not empty), return 0 is suggested
 	}
 #endif
 
@@ -135,6 +137,8 @@ protected:
 		//following statement can avoid one memory replication if the type of out_msg_type and in_msg_type are identical.
 		ascs::do_something_to_all(tmp_can, [this](out_msg_type& msg) {this->send_msg(std::move(msg), true);});
 		return 1;
+		//if we indeed handled some messages, do return 1
+		//if we handled nothing, return 1 is also okey but will very slightly impact performance, return 0 is suggested
 	}
 #else
 	//following statement can avoid one memory replication if the type of out_msg_type and in_msg_type are identical.

examples/file_client/file_client.h

@@ -65,9 +65,46 @@ public:
 
 protected:
 	//msg handling
+#ifdef ASCS_SYNC_DISPATCH
+	virtual size_t on_msg(list<out_msg_type>& msg_can)
+	{
+		//ascs will never append empty message automatically for on_msg (if no message nor error returned from the unpacker) even with
+		// macro ASCS_PASSIVE_RECV, but will do it for on_msg_handle (with macro ASCS_PASSIVE_RECV), please note.
+		if (msg_can.empty())
+			handle_msg(out_msg_type()); //we need empty message as a notification, it's just our business logic.
+		else
+		{
+			ascs::do_something_to_all(msg_can, [this](out_msg_type& msg) {this->handle_msg(msg);});
+			msg_can.clear();
+		}
+
+		recv_msg(); //we always handled all messages, so calling recv_msg() at here is very reasonable.
+		return 1;
+		//if we indeed handled some messages, do return 1
+		//if we handled nothing, return 1 is also okey but will very slightly impact performance (if msg_can is not empty), return 0 is suggested
+	}
+#endif
+#ifdef ASCS_DISPATCH_BATCH_MSG
+	virtual size_t on_msg_handle(out_queue_type& msg_can)
+	{
+		//msg_can can't be empty, with macro ASCS_PASSIVE_RECV, ascs will append an empty message automatically for on_msg_handle if no message nor
+		// error returned from the unpacker to provide a chance to call recv_msg (calling recv_msg out of on_msg and on_msg_handle is forbidden), please note.
+		assert(!msg_can.empty());
+		out_container_type tmp_can;
+		msg_can.swap(tmp_can);
+
+		ascs::do_something_to_all(tmp_can, [this](out_msg_type& msg) {this->handle_msg(msg);});
+
+		recv_msg(); //we always handled all messages, so calling recv_msg() at here is very reasonable.
+		return 1;
+		//if we indeed handled some messages, do return 1
+		//if we handled nothing, return 1 is also okey but will very slightly impact performance, return 0 is suggested
+	}
+#else
 	virtual bool on_msg_handle(out_msg_type& msg) {handle_msg(msg); if (0 == get_pending_recv_msg_size()) recv_msg(); return true;}
 	//only raise recv_msg() invocation after recveiving buffer becomes empty, it's very important, otherwise we must use mutex to guarantee that at any time,
 	//there only exists one or zero asynchronous reception.
+#endif
 	//msg handling end
 
 	virtual void on_connect()

include/ascs/container.h

@@ -114,6 +114,8 @@ public:
 	{
 		if (0 == size_in_byte)
 			size_in_byte = ascs::get_size_in_byte(src);
+		else
+			assert(ascs::get_size_in_byte(src) == size_in_byte);
 
 		this->splice(this->end(), src);
 		total_size += size_in_byte;

include/ascs/tcp/socket.h

@@ -269,7 +269,7 @@ private:
 				on_unpack_error(); //the user will decide whether to reset the unpacker or not in this callback
 
 #ifdef ASCS_PASSIVE_RECV
-			reading = false; //clear reading flag before call handle_msg() to make sure that recv_msg() can be called successfully in on_msg_handle()
+			reading = false; //clear reading flag before calling handle_msg() to make sure that recv_msg() is available in on_msg() and on_msg_handle()
 #endif
 			if (handle_msg()) //if macro ASCS_PASSIVE_RECV been defined, handle_msg will always return false
 				do_recv_msg(); //receive msg in sequence
@@ -277,7 +277,7 @@ private:
 		else
 		{
 #ifdef ASCS_PASSIVE_RECV
-			reading = false; //clear reading flag before call handle_msg() to make sure that recv_msg() can be called successfully in on_msg_handle()
+			reading = false; //clear reading flag before calling handle_msg() to make sure that recv_msg() is available in on_msg() and on_msg_handle()
 #endif
 			if (ec)
 			{