def _read_chunk(self, buff):
    while len(buff) < self.HEADER_LENGTH:
      buff += self._sock.recv(self.BUFF_SIZE)

    payload_length, command = struct.unpack(self.HEADER_FMT, buff[:self.HEADER_LENGTH])
    buff = buff[self.HEADER_LENGTH:]
    while len(buff) < payload_length:
      buff += self._sock.recv(self.BUFF_SIZE)

    payload = buff[:payload_length]
    rest = buff[payload_length:]
    return command, payload, rest