Identify and separate the data from Datagrampacke's Data Packet using java

Question

Hi Currently I am working on Android that communicates with Healthcare device through bluetooth. The Healthcare device can send data packets like this format

Now I want to know, how can I identify the LSB , Acces code, Header , Msb and Payload separately. and how can I retrieve the data from this packets. Really I am new for this kind of data packets development. I have googled, but I got theoretical solutions only. Also I want to know, whether I can use Datagrampacket or someother 3rd party API. Kindly someone suggest me some ideas and tutorial for this. Thanks in advance.

Answer 1

Try to use the following method:

(2475 bits? it maybe should be 2472 or 2480, or if header is 54 bits, here should be 2474 bits) // read bytes

public byte[] readBytes(InputStream inputStream, int length)
        throws IOException {
    byte[] data = new byte[length];
    int len = inputStream.read(data);
    if (len != length) {
        throw new IOException("Read the end of stream.");
    }
    return data;
}


//Get Header data
byte[] headerData = readBytes(inputStream, 9);

// I think header data need to parse again, its structure should look like the following format:
// | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |
// |  Version  | Type  | other values  |
// You can parse them to use headerData


// #######################################
// write bytes
public class ByteWriter {
    private final ByteArrayOutputStream outputStream = new ByteArrayOutputStream();

    public void writeBytes(byte[] data) {
        try {
            outputStream.write(data);
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }

    public byte[] getBytes() {
        return outputStream.toByteArray();
    }
}

Answer 2

DataInputStream is your friend here. Wrap it around a ByteArrayInputStream wrapped around the DatagramPacket's data, offset, and length. Then use readBytes() into a 9-byte array to get the access code, readBytes() into a 7-byte array to get the header, and the rest is the payload.

EDIT:

Is the header really 54 bits? Surely that should be 56?