## POEx::ZMQ::Socket
  ## Send queue handling
    * EAGAIN, EINTR, EFSM should cause a requeue
    * max_send_retries
    * max_queue_size
    * queue_overflow_action ? drop / warn+drop / die
    * retry_overflow_action ? drop / warn+drop / die

  ## IPv6 helper
    * ->ipv6() attr
      automatically (v3.3+ ? set ZMQ_IPV6 : unset ZMQ_IPV4ONLY) after build

  ## Monitor support

  ## Curve encryption support

  #? SSH tunnelling helper?

#? Per-socket classes w/ POE::Filter integration
