This is the server code for the udp server/client program . There are no errors except when you run the program the ff error occurs:
Exception in thread "main" java.lang.NullPointerException
at udptry2.UDPServerbackup2.main(UDPServerbackup2.java:44)
Java Result: 1
the client side works how it should just this part of the program
package udptry2;
import java.io.*;
import java.net.*;
import java.util.*;
import java.lang.*;
import java.lang.String;
class UDPServerbackup2
{
public static void main(String args[]) throws Exception
{
Scanner x = null ;
DatagramSocket serverSocket = new DatagramSocket(6666);
byte[] receiveData = new byte[1024];
byte[] receiveData2 = new byte[1024];
byte[] sendData = new byte[1024];
byte[] sendData2 = new byte[1024];
//String Serverdata="1234";
int sendGrade;
int serverdata[] = {1111,2222,3333,4444,5555};
int serverdata2[] = null ;
int grades[] = {50,60,70,80,90};
int grades2[] = {50,60,70,80,90};
boolean flag1 = true;
int i;
//readfile r = new readfile();
//r.openfile();
try{
x = new Scanner(new File("serverdata.txt"));
}catch(Exception e)
{
System.out.println("File not found"+e);
}//end of catch
while(x.hasNext())
{
for(int j=0;j<serverdata2.length;j++)
{
serverdata2[j] = x.nextInt();
grades2[j]=x.nextInt();
System.out.println("id: "+ serverdata2[j] +"result: "+ grades2[j]);
}
}//end of while
x.close();
// r.closefile();
System.out.println("=============");
System.out.println("UDP Server Starting");
System.out.println("=============");
while(flag1 != false)
{
DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
serverSocket.receive(receivePacket);
String sentence = new String(receivePacket.getData());
sentence=sentence.trim();
System.out.println("RECEIVED: " + sentence);
InetAddress IPAddress = receivePacket.getAddress();
int port = receivePacket.getPort();
String ack = "Client....This is Server...connection established successfully ";
sendData = ack.getBytes();
DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, port);
serverSocket.send(sendPacket);
DatagramPacket receivePacket2 = new DatagramPacket(receiveData2, receiveData2.length); //new buffer
serverSocket.receive(receivePacket2);
String idnumber = new String(receivePacket2.getData());
idnumber = idnumber.trim();
int a = Integer.parseInt(idnumber);
System.out.println("id number you typed was: " + a);
for(i=0;i<serverdata.length;i++)
{
if (a == serverdata[i])
{
System.out.println("Grade is: "+grades[i]+"%");
sendGrade = grades[i];
String sendGradestring = Integer.toString(sendGrade);
sendData2=sendGradestring.getBytes();
DatagramPacket sendPacket2 = new DatagramPacket(sendData2, sendData2.length, IPAddress, port);
serverSocket.send(sendPacket2);
break;
}
} //end of for
}//end of while
}//end of main
}//end of class