title: What is the difference between synchronous and asynchronous transmission in TCP/ IP socket programming?
body: <p>I am new to C++ and I am trying to develop a client-server application based on the boost::asio library. I am (still) not able to understand properly the difference between sync and async modes. I've previously studied web protocol services such as HTTP and AJAX. From <a href="http://wiki.answers.com/Q/Why_http_is_asynchronous" rel="noreferrer">this explanation</a>, it's clear that HTTP is synchronous and AJAX is asynchronous. What is the difference in TCP socket communication in terms of sync and async? And which mode is better from the perspective of enterprise-level multi-threaded application development, and why?</p>
  
  <p>As I understand synchronous mode, the client blocks for a while until it receives the packet/ data message from the server. And in async mode, the client carries out another operation without blocking the current operation. Why is this different? Is async synonymous with UDP? It seems it doesn't care if it receives transmission acknowledgement.</p>