import java.io.*;
import java.net.*;
import java.util.zip.CRC32;
import java.util.zip.Checksum;

public class rConUDPTool {

    public static void main (String args[]) throws Exception{
        System.out.println("Opening Connection...");

        connect();

    }

    protected static void connect() throws Exception{

        String pass = "xxxxx";

        DatagramSocket clientSocket = new DatagramSocket();
        InetAddress IPAddress = InetAddress.getByName("localhost");
        byte[] sendData = new byte[1024];
        byte[] receiveData = new byte[1024];

        String sentence = "BE";
        sentence += StrToHex("FF00") + pass;

        String header = "BE";
        String hash = StrToHex("FF00") + pass;
        String hashL = getCRC(hash.getBytes());

        hash = StrToHex(hashL);
        char[] HashPreReversed = hash.toCharArray();

        // reverse hash array
        int idx = 0;
        char[] HashReversed = new char[HashPreReversed.length];
        for (int i = HashPreReversed.length - 1; i >= 0; i--){
            HashReversed[idx] = HashPreReversed[i];
            idx++;
        }
        hash = HashReversed.toString();

        header += hash;

        String packet = header + StrToHex("FF00") + pass;

        sendData = packet.getBytes();

        DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, 2302);
        clientSocket.send(sendPacket);

        DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
        clientSocket.receive(receivePacket);

        String modifiedSentence = new String(receivePacket.getData());
        System.out.println("FROM SERVER:" + modifiedSentence);
        clientSocket.close();



    }


    protected static String getCRC(byte bs[]){


        byte bytes[] = bs;
        Checksum ckSum = new CRC32();

        ckSum.update(bytes,0,bytes.length);

        String returnValue = Long.toString(ckSum.getValue());

        return returnValue;
    }

    protected static String StrToHex(String str){
        char[] chars = str.toCharArray();

        StringBuffer hex = new StringBuffer();
        for(int i = 0; i <chars.length; i++){
            hex.append(Integer.toHexString((int)chars[i]));
        }

        return hex.toString();
    }
}