title: ZMQ sockets with custom load-balancing
body: <p>I looked at ZMQ PUSH/PULL sockets and even though I quite like the simplicity (especially compared to custom fragmentation/ack I am implementing right now in a system over UDP sockets), I would like to have custom load balancing instead of the naive round-robin (I believe) that ZMQ PUSH/PULL sockets are using.</p>
  
  <p>I am new to ZQM and not sure how I can implement it using ZMQ sockets and if it's even possible at all. What I would ideally like is, the serving PUSH socket (or some other socket type) determines (based on the messages etc.) which machine to send the message to.</p>
  
  <p>So my questions are:</p>
  
  <ol>
  <li>Is this possible?</li>
  <li>If so, what ZMQ pattern would work best for it?</li>
  <li>How can I use those sockets?</li>
  </ol>