getpacket method
Implementation
int getpacket(Uint8List packet) {
//construct the packet = header + payload
for (int i = 0; i < HEADER_SIZE; i++) packet[i] = header[i];
for (int i = 0; i < payload_size; i++) packet[i + HEADER_SIZE] = payload[i];
//return total size of the packet
return (payload_size + HEADER_SIZE);
}