code: def socketBinaryStream(self, hostname, port, length):
          
          deserializer = TCPDeserializer(self._context)
          tcp_binary_stream = TCPBinaryStream(length)
          tcp_binary_stream.listen(port, hostname)
          self._on_stop_cb.append(tcp_binary_stream.stop)
          return DStream(tcp_binary_stream, self, deserializer)
docs: Create a TCP socket server for binary input.
  
          .. warning::
              This is not part of the PySpark API.
  
          :param string hostname: Hostname of TCP server.
          :param int port: Port of TCP server.
          :param length:
              Message length. Length in bytes or a format string for
              ``struct.unpack()``.
  
              For variable length messages where the message length is sent right
              before the message itself, ``length`` is
              a format string that can be passed to ``struct.unpack()``.
              For example, use ``length='<I'`` for a little-endian
              (standard on x86) 32-bit unsigned int.
          :rtype: DStream