0x81 0x80

public static void main(String[] args) {
		String ida = "";
		String volta = "";
		String hex = "81800001000100030000";
		String wBuffer = "";
		for (int i = 0; i < hex.length(); i = i + 2)
			wBuffer = wBuffer
					+ (char) Integer.parseInt(hex.substring(i, i + 2), 16);
		byte[] sendData;
		sendData = wBuffer.getBytes();
		for (char ch : wBuffer.toCharArray())
			volta += Integer.toHexString(ch) + " ";
		System.out.print(volta + "\n");
		DatagramPacket sendPacket = new DatagramPacket(sendData,
				sendData.length);
		sendPacket.setData(sendData);
		String fa = new String(((byte[]) sendPacket.getData()));
		volta = "";
		for (char ch : fa.toCharArray())
			volta += Integer.toHexString(ch) + " ";
		System.out.print(volta);

	}