title: Communication from client to server in Java
body: <h2>The system</h2>
  
  <p>For a school project, we need to build a system consisting of:</p>
  
  <ol>
  <li>Two Raspberry Pi (communicating via Ethernet locally, a client and a server)</li>
  <li>The server Pi (Tomcat is imposed) must generate a web page that evolves according to the inputs of a controller that is connected to the Pi client.</li>
  <li>The implementation is done using Java and Java EE.</li>
  </ol>
  
  <p>Here is the system at high level:
  <a href="http://i.stack.imgur.com/CXLPp.png" rel="nofollow">The system needed (high level)</a></p>
  
  <h2>The problem</h2>
  
  <p>The problem me and my colleagues are facing is that we want the <em>server</em> to update the web page when the <em>client</em> changes (i.e a button on the controller is pressed). Usually, it seems, the communication is in the other way, that is, from server to client.</p>
  
  <p><em>Is there any way to do this in Java?</em></p>
  
  <p>Notes:</p>
  
  <ul>
  <li>The web browser and the client are not on the same machine necessarily.</li>
  </ul>