title: Why ZeroMQ PUB/SUB example in python does not receive any messages?
body: <p>I was trying to run ZeroMQ <code>PUB/SUB</code>-archetype example in python (<a href="http://zguide.zeromq.org/py:wuserver" rel="nofollow noreferrer">wuserver</a>, <a href="http://zguide.zeromq.org/py:wuclient" rel="nofollow noreferrer">wuclient</a>) from the guide and it does not work for me.</p>
  
  <p>I tried it on an Ubuntu VM. I am running <code>python3.6.1</code> with <code>pyzmq.__version__ == 16.0.3</code> on <code>ubuntu 16.10</code> (in VM). If I change sockets' archetypes from <code>PUB/SUB</code> to <code>PUSH/PULL</code>, the client starts getting messages, as expected. </p>
  
  <ul>
  <li>What am I missing?</li>
  <li>And what can I do to find out the cause of this unexpected behavior?</li>
  </ul>
  
  <p>I start a <code>SUB</code>-client before the <code>PUB</code>-server (I've tried the other way around too) but <code>SUB</code> never gets any message.</p>