its eror:

Basic Client Socket Programming Socket Connected Error msg: java.io.FileNotFoundException: Hello (Byle bir dosya ya da dizin yok) Hash code generated: null Picked up JAVA_TOOL_OPTIONS: -javaagent:/usr/share/java/jayatanaag.jar Exception in thread "main" java.lang.NullPointerException at java.io.Writer.write(Writer.java:157) at Udp.ClientSocket.main(ClientSocket.java:51)

pls help me why this code dont run

package Udp;

import java.io.BufferedReader; import java.io.BufferedWriter; import java.io.DataOutputStream; import java.io.FileInputStream; import java.io.FileWriter; import java.io.IOException; import java.io.InputStreamReader; import java.io.PrintWriter; import java.net.Socket; import java.net.UnknownHostException; import java.util.Scanner;

// Class Client Socket public class ClientSocket { public static void main(String[] args) throws IOException { // show main Menu System.out.println("Basic Client Socket Programming"); // Socket Variables Socket clientSocket = null; // for sending and receiving of data PrintWriter outputStream = null; // for sending data BufferedReader inputStream = null; // for receiving data // Create and open socket // Connection to 127.0.0.1, port num=2001 try { clientSocket = new Socket("localhost",7777); outputStream = new PrintWriter(clientSocket.getOutputStream(), true); inputStream = new BufferedReader(new InputStreamReader(clientSocket.getInputStream())); } catch (UnknownHostException e) { System.err.println("Don't know about host: 127.0.0.1"); return; } catch (IOException e) { System.err.println("Couldn't get I/O for the connection to: 127.0.0.1"); return; } // check if connection is successful if ((clientSocket == null) || (outputStream == null) || (inputStream == null)) { System.err.println("Socket Connection not successfull"); return; } else { System.out.println("Socket Connected"); } // generate MD5 and send data String hash = MD5.doMD5("Hello"); System.out.println("Hash code generated: " + hash); // outputStream.println("Hello ||" + hash); // creates a new BufferWriter to write the hash value and the text // message into the txt file. BufferedWriter out = new BufferedWriter(new FileWriter("hashedCode.txt")); out.write(hash); // writes the hash code to the file out.close(); // close the bufferreader // Send the file to the server

FileInputStream fin = new FileInputStream("hashedCode.txt"); Scanner sc = new Scanner(fin);

DataOutputStream out1 = new DataOutputStream(clientSocket.getOutputStream()); while (sc.hasNextLine()) { String line = sc.nextLine(); out1.writeUTF(line); } sc.close(); out1.close();

// receiving data String rcvData; rcvData = inputStream.readLine(); System.out.println(rcvData);

// close connections try

{ outputStream.close(); inputStream.close(); clientSocket.close(); System.out.println("Connection closed."); } catch (

UnknownHostException e)

{ System.err.println("Trying to connect to unknown host: " + e); } catch (

IOException e)

{ System.err.println("IOException: " + e); } // exit program return; } }

package Udp;

//Imports import java.io.*; import java.net.*;

public class serverSocket { public static void main(String[] args) throws IOException {

// Socket Variables ServerSocket serverSocket = null; // for listen for connection Socket rcvSocket = null; // for sending n rcving data DataOutputStream outputStream = null; // for sending data DataInputStream inputStream = null; // for receiving data // try to open a socket to listen for incoming data // port number must match the one that the client is connecting to try { serverSocket = new ServerSocket(7777); } catch (IOException e) { System.err.println(e); } // creating a socket to rcv incoming data while (true) { try { System.out.println("Listening"); rcvSocket = serverSocket.accept(); System.out.println("Connected"); PrintWriter out = new PrintWriter(rcvSocket.getOutputStream(), true); BufferedReader in = new BufferedReader(new InputStreamReader(rcvSocket.getInputStream())); // initiate conversation with client String rcvData = in.readLine(); System.out.println("Rcv Data: " + rcvData); out.println(rcvData); } catch (IOException e) { System.err.println(e); } } } }

package Udp;

import java.io.FileInputStream; import java.security.MessageDigest;

public class MD5 { private static String checkSumValue;

public String getCheckSumValue() { return checkSumValue; }

public void setCheckSumValue(String checkSumValue) { this.checkSumValue = checkSumValue; }

public static String doMD5(String path) { try { MessageDigest md = MessageDigest.getInstance("MD5"); FileInputStream fis = new FileInputStream(path); byte[] dataBytes = new byte[1024]; int nread = 0; while ((nread = fis.read(dataBytes)) != -1) { md.update(dataBytes, 0, nread); } ; byte[] mdbytes = md.digest(); StringBuffer sb = new StringBuffer(); for (int i = 0; i < mdbytes.length; i++) { sb.append(Integer.toString((mdbytes[i] & 0xff) + 0x100, 16).substring(1)); } checkSumValue = sb.toString(); System.out.println("Digest(in hex format):: " + checkSumValue); } catch (Exception ex) { System.out.println("Error msg: " + ex); } return checkSumValue; } }