title: is it safe to recv() and send() on one socket concurrently?
body: <p>I remember having read somewhere that a socket can be regarded as two independent half-duplex channels. Does it mean that <code>recv()</code> and <code>send()</code> of the same socket are actually irrelevant? </p>
  
  <ul>
  <li>if so,  is it by definition or
  implementation-specific?  </li>
  <li>if not, how the two interfere with each other?</li>
  </ul>
  
  <p>thanks.</p>