def _send_resolve_ptr_request(self):
        "sends RESOLVE_PTR request (Tor custom)"
        addr_type = 0x04 if isinstance(self._addr, ipaddress.IPv4Address) else 0x01
        encoded_host = inet_aton(self._addr.host)
        self._data_to_send(
            struct.pack(
                '!BBBB4sH',
                5,                   # version
                0xF1,                # command
                0x00,                # reserved
                addr_type,
                encoded_host,
                0,                   # port; unused? SOCKS is fun
            )
        )
sends RESOLVE_PTR request (Tor custom)