title: How send arraybuffer as binary via Websocket?
body: <p>I am working on a project with Mozilla Europe. In this project, I use websocket by Worlize (server-side) and Mozilla (client side), Node.js to try to upload files from a client to a server.<br>
  My present goal is to send a <code>arraybuffer</code> of the file to the server. Create the arraybuffer and send it is fine.<br>
  But my server tells me that <code>arraybuffer</code> is a utf8 message and not a binary message.  </p>
  
  <p>Do I misunderstand something? If not, how can i correct that?  </p>
  
  <p>Client side:</p>
  
  <pre><code>    reader = new FileReader();
      reader.readAsArrayBuffer(file);
      reader.onload = function(e) {
          connection.send(e.target.result); 
      };
  </code></pre>
  
  <p>Server side:</p>
  
  <pre><code>ws.on('message', function(message,flags) {
  if (!flags.binary) {
      //some code
  }
  else {
      console.log('It\'s a binary');
  }
  </code></pre>
  
  <p>I try with <code>Blob</code> too, same result. The binary part is invisible.</p>