Sending unsigned bytes using DatagramPacket

[sranil]

Hi All,

As Java doesn't support unsigned bytes, can you please tell me how to send the unsigned byte using DatagramPacket.

Regards,
Anil

[neilcoffey]

Anil, the unsigned/signed distinction is only relevant when you're interpreting the bytes. Otherwise, a byte is just a byte. So, say you want to send the byte value 200, you just add (byte) 200 to the array of data you're sending. At the other end, to read the signed byte as though it were unsigned, just and with 0xff. So:

// sender
byte[] dataToSend = ...
dataToSend[0] = (byte) 200;

and then the receiver:

byte[] receivedData = ...
int firstByte = receivedData[0] & 0xff;

On the receiving end, because the byte type stores -128 to 127, we put the value into an int, so that values between 128 and 255 can be represented.

You may also be interested in my article on the Java equivalent of 'unsigned'.

[Steve11235]

The ByteBuffer class is also very helpful, although it doesn't address this exact issue. What it does provide is character set encode/decode and assistance putting and getting various primitives into and out of a byte[].