class Puma::Server

def closed_socket?(socket)
  skt = socket.to_io
  return false unless skt.kind_of?(TCPSocket) && @precheck_closing
  begin
    tcp_info = skt.getsockopt(Socket::IPPROTO_TCP, Socket::TCP_INFO)
  rescue IOError, SystemCallError
    Puma::Util.purge_interrupt_queue
    @precheck_closing = false
    false
  else
    state = tcp_info.unpack(UNPACK_TCP_STATE_FROM_TCP_INFO)[0]
    # TIME_WAIT: 6, CLOSE: 7, CLOSE_WAIT: 8, LAST_ACK: 9, CLOSING: 11
    (state >= 6 && state <= 9) || state == 11
  end
end