title: How to drop inactive/disconnected peers in ZMQ
body: <p>I have a client/server setup in which clients send a single request message to the server and gets a bunch of data messages back.
  The server is implemented using a ROUTER socket and the clients using a DEALER. The communication is asynchronous.
  The clients are typically iPads/iPhones and they connect over wifi so the connection is not 100% reliable.</p>
  
  <p>The issue I’m concern about is if the client connects to the server and sends a request for data but before the response messages are delivered back the communication goes down (e.g. out of wifi coverage).</p>
  
  <p>In this case the messages will be queued up on the server side waiting for the client to reconnect. That is fine for a short time but eventually I would like to drop the messages and the connection to release resources.</p>
  
  <p>By checking activity/timeouts it would be possible in the server and the client applications to identify that the connection is gone. The client can shutdown the socket and in this way free resources but how can it be done in the server?  </p>