unsigned char payload_bin[] = {
  0x00, 0x01, 0x00, 0x00, 0x21, 0x12, 0xa4, 0x42, 0x00, 0x00, 0x00, 0x00,
  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
};
unsigned int payload_bin_len = 20;