title: ZMQ subscriber filtering
body: <p>According to the following discussion</p>
  
  <p><a href="https://stackoverflow.com/questions/25696501/can-zmq-publish-message-to-specific-client-by-pub-sub-socket">Can ZMQ publish message to specific client by pub-sub socket?</a></p>
  
  <p>there seems to be no possibility of preventing a subscriber from receiving all messages when he does not provide a filter.</p>
  
  <p><strong>Is it possible</strong> that a subscriber that provides no filter will not receive any messages? I.e., <strong>a subscriber does only receive messages, if he knows an exact filter</strong> (no wildcards, etc).</p>