Greetings, A server that I'm communicating with sends two types of messages identified by an ID. The first message type is sent automatically on specific events. The second type is sent in response to commands. I want to provide an interface that notifies the user when events occur (asynchronously) and at the same time enable performing commands. My first implementation did this (pseudocode): // In initialization socket.async_receive(buffer, event_handler); // In send_command socket.send(command_buffer); socket.receive_async(response_buffer, user_response_handler); event_handler() { user_event_handler(); socket.async_receive(buffer, event_handler); } The problem here is that 'event_handler' might (or will?) receive the response message. An additional problem is that these messages have no specific order. In other words, the following sequence might occur: - Send command (A) - Send command (B) - Receive event notification - Receive response (A) - Receive response (B) A possible solution might be the following: // In initialization socket.async_receive(buffer, msg_handler); // In send_command socket.send(command_buffer); handlers_queue.enqueue(user_command_handler); socket.receive_async(response_buffer, msg_handler); // Line(3) msg_handler() { if (event) user_event_handler(); else handlers_queue.dequeue() (); // Call first user handler socket.async_receive(buffer, msg_handler); } I want to know if boost::asio provides a better way to solve this problem. I'm particularly interested if writing a custom io service can help me in this situation. Thanks you, -- Abdo Haji-Ali Programmer In|Framez