java net

import java.io.FileInputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.MulticastSocket;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.SocketException;
import java.net.UnknownHostException;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.Signature;
import java.security.SignedObject;

public class MainSocket {

 public MainSocket() {
  //Transmission control protocol  user datagram protocol
  //DatagramSocket udp
  //send close
  //sock_stream  sock_dgram  sock_raw
  //DatagramPacket
  //InetAddress
  try {
   byte[] buf=new byte[1024];
   DatagramSocket ds=new DatagramSocket();
   InetAddress add=null;
   try {
    add = InetAddress.getByName("www.www");
   } catch (UnknownHostException e1) {    
    e1.printStackTrace();
   }
   try {
    ds.send(new DatagramPacket(buf,buf.length,add,5555));
   } catch (IOException e) {    
    e.printStackTrace();
   }   
   DatagramPacket dp=new DatagramPacket(buf,1024);
   try {
    ds.receive(dp);
   } catch (IOException e) {
    
    e.printStackTrace();
   }
   new String(dp.getData(),0,dp.getLength());
   dp.getAddress().getHostAddress();
  } catch (SocketException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
  //ServerSocket  tcp
  
 }

 public void server(){
  byte[] buf=new byte[1024];
  InetAddress add=null;
  DatagramSocket ds=null;
  DatagramPacket dp=null;
  try {
   add = InetAddress.getByName("www.www");
   dp=new DatagramPacket(buf,1024,add,5555);
   ds = new DatagramSocket(5555);
   ds.send(dp);
  } catch (SocketException e) {   
   e.printStackTrace();
  } catch (IOException e) {   
   e.printStackTrace();
  }
  
 }
 
 //多点传送 multi send
 public void mulit(){
  try {
   byte[] buf=new byte[1024];
   InetAddress group=InetAddress.getByName("");
   MulticastSocket ms=new MulticastSocket(5555);
   ms.joinGroup(group);
   DatagramPacket dp=new DatagramPacket(buf,buf.length,group,5555);
   ms.send(dp);
   ms.leaveGroup(group);
  } catch (IOException e) {
   
   e.printStackTrace();
  }
 }
 
 public void client(){
  byte[] buf=new byte[1024];
  DatagramSocket ds;
  DatagramPacket dp=new DatagramPacket(buf,buf.length);
  try {
   ds = new DatagramSocket(5555);
   ds.receive(dp);
  } catch (SocketException e) {   
   e.printStackTrace();
  } catch (IOException e) {   
   e.printStackTrace();
  }
  
  
 }
 /**
  * @param args
  */
 public static void main(String[] args) throws Exception{
  Socket s=null;
  ObjectOutputStream os=null;
  s=new Socket("pureajava",40000);
  os=new ObjectOutputStream(s.getOutputStream());
  //generate public and private keys
  KeyPairGenerator kgen=KeyPairGenerator.getInstance("DSA");
  kgen.initialize(256);
  KeyPair kpair=kgen.generateKeyPair();
  
  //generate a  signature
  Signature sig=Signature.getInstance("SHA/DSA");
  PublicKey pub=kpair.getPublic();
  PrivateKey priv=kpair.getPrivate();
  sig.initSign(priv);
  
  //Read a file and compute a signature
  FileInputStream fis =new FileInputStream("demo");
  byte arr[]= new byte[fis.available()];
  fis.read(arr);
  sig.update(arr);
  
  //send the signedobject on the wire
  SignedObject obj=new SignedObject(arr,priv,sig);
//   new SignedObject(arr,sig.sign(),pub);
  os.writeObject(obj);
  fis.close();
  os.close();
  s.close();
  
  //service
  ServerSocket service=new ServerSocket(4000);
  Socket clientSocket=service.accept();
  ObjectInputStream ois=new ObjectInputStream(clientSocket.getInputStream());
  SignedObject ob=(SignedObject)ois.readObject();
  //generate object's signature
  Signature sign=Signature.getInstance("SHA/DSA");
  sign.initVerify(pub);
  sign.update(ob.getSignature());
  //verify the signature
  boolean valid=sign.verify(ob.getSignature());
 }

}