title: How does upstream and downstream handlers work in Netty?
body: <p>I'm new to <a href="https://netty.io/" rel="nofollow noreferrer">Netty</a> and don't really understand the flow of handlers in it. What I want to know is the difference between the <code>Upstream</code> and <code>Downstream</code> handlers.</p>
  <ul>
  <li>Why can't we intercept the message in downstream handlers as we do in
  upstream?</li>
  <li>Do downstream and upstream mean the same as in normal terms?</li>
  </ul>