title: Recovering from zmq.error.ZMQError: Address already in use
body: <p>I hit Ctrl-C while running a <code>PAIR</code> pattern (non-blocking client servers) connection with ZMQ. Later when I tried running the <code>REQ-REP</code> (blocking client single server connection) pattern, I keep getting the <code>Address already in use</code> error. I have tried running netstat with <code>netstat -ltnp | grep :&lt;my port&gt;</code> but that does not list any process. </p>
  
  <p>So who exactly is using this address? </p>
  
  <p>Also how does one gracefully shutdown socket connections like these?</p>