java.lang.NullPointerException

[Markus85]

bisognerebbe vedere meglio il contesto.

Eccolo :

package appello19Febbraio2014; // OK


import java.util.*;
import java.io.*;
import java.net.*;
import java.security.*;
import java.security.spec.*;
import javax.crypto.*;




class Host {
    
    private SendKey sk;
    private KeyPair kp;
    private Cipher cipher , decipher;
    private int UDPPort;
    
    public Host(int skPort){
        
        try{
        sk = new SendKey(skPort);
        sk.start();
        DatagramSocket dSocket = new DatagramSocket(UDPPort);
        
        }catch(Exception err){
            err.printStackTrace();
        }
        
    }//COSTRUTTORE
    
    class SendKey extends Thread{
        
        private ServerSocket sSocket;
        private int skPort;
        
        public SendKey(int skPort){
            
        this.skPort = skPort;
        
        try{
            sSocket = new ServerSocket(skPort);
            
        }catch(Exception err){
            err.printStackTrace();
         }
        
        }
        
        public void run(){
            
            try{
                while(true){
                    
                    Socket s = sSocket.accept();
                    InputStream in = s.getInputStream();
                    in.read();
                    
                    KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA");
                    kpg.initialize(1000);
                    kp = kpg.generateKeyPair();
                    
                    decipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
                    decipher.init(Cipher.DECRYPT_MODE , kp.getPrivate());
                    cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
                    cipher.init(Cipher.ENCRYPT_MODE , kp.getPrivate());
                    
                    OutputStream out = s.getOutputStream();
                    out.write(kp.getPublic().getEncoded());
                }
            }catch(Exception err){
                err.printStackTrace();
            }
        }
    }//THREAD SEND KEY
    
    class gestisciRichieste extends Thread {
        
        private Socket s;
        private DatagramSocket dSocket;
        private int UDPPort;
        
        public gestisciRichieste(Socket s , int UDPPort){
            
            try{
            this.s = s;
            this.UDPPort = UDPPort;
            DatagramSocket dSocket = new DatagramSocket(UDPPort);
            this.start();
            
            }catch(Exception err){
                err.printStackTrace();
            }
            
        }
        
        public void run(){
            
            try{
                while(true){
                    
                    InputStream in = s.getInputStream();
                    byte [] richiestaByte = new byte [1000];
                    int numByte = in.read(richiestaByte);
                    richiestaByte = Arrays.copyOf(richiestaByte , numByte);
                    
                    String richiesta = new String(decipher.doFinal(richiestaByte));
                    int pos = richiesta.indexOf("@");
                    String ip = richiesta.substring(0,pos);
                    String messaggio = richiesta.substring(pos+1);
                    
                    in.close();
                    
                    byte [] buf = cipher.doFinal(messaggio.getBytes());
                    InetAddress clientAdd = InetAddress.getByName(ip);
                    DatagramPacket packet = new DatagramPacket(buf , buf.length , clientAdd , UDPPort);
                    dSocket.send(packet);
                }
            }catch(Exception err){
                err.printStackTrace();
            }
        }
    }// THREAD GESTISCI RICHIESTE
    
    public static void main (String [] args){
        
        try{
            int skPort = 6900;
            ServerSocket servSocket = new ServerSocket(6800);
            int UDPPort = 7700;
            
            Host host = new Host(skPort);
            
            while(true){
                
                Socket s = servSocket.accept();
                gestisciRichieste gr = host.new gestisciRichieste(s , UDPPort);
                
            }
        }catch(Exception err){
            err.printStackTrace();
        }
        
    }//MAIN


}//HOST

L'invio del pacchetto è nella classe gestisciRichieste