title: ZeroMQ PUSH/PULL and lost message
body: <p>I'm making use of ZeroMQ from .NET and got stuck trying to fix a weird issue.
  I've got a socket of type PUSH and one of type PULL over TCP.
  When the client disconnects, the server is still able to to send a message (note that no flags are passed to the Socket.Send method) which gets completely lots before starting to block and waiting for the client to reconnect and delivering messages I try to send afterwards.</p>
  
  <p>How can I avoid losing the message (or in the worst case test if a client is connected and if not send a dummy message which I can afford losing)?</p>
  
  <p>Thanks in advance!</p>
  
  <p><strong>Edit:</strong> further testing reveals that if I wait 1 second after sending the first message after disconnection by the client, the second one will block, but if I don't wait at all I can send as many messages as I want and they'll all get lost. That's quite confusing...</p>