class Protobuf::Rpc::Connectors::Zmq

def host_alive?(host)
  return true unless ping_port_enabled?
  if (last_response = self.class.ping_port_responses[host])
    if (Time.now.to_i - last_response[:at]) <= host_alive_check_interval
      return last_response[:ping_port_open]
    end
  end
  ping_port_open = ping_port_open?(host)
  self.class.ping_port_responses[host] = {
    :at => Time.now.to_i,
    :ping_port_open => ping_port_open,
  }
  ping_port_open
end