java UDP

package test;
import java.net.*;
public class Dgram {
    public static DatagramPacket toDatagram(
            String s,InetAddress destIA,int destPort){
        byte[] buf = new byte[s.length() + 1];
        buf = s.getBytes();
        return new DatagramPacket(buf,buf.length,destIA,destPort);
    }
    public static String toString(DatagramPacket p){
        return new String(p.getData(),0,p.getLength());
    }
    
}

//: ChatterClient.java 
// Tests the ChatterServer by starting multiple  
// clients, each of which sends datagrams. 
package test;
import java.lang.Thread; 
import java.net.*; 
import java.io.*; 
 
public class ChatterClient extends Thread { 
  // Can listen & send on the same socket: 
  private DatagramSocket s; 
  private InetAddress hostAddress; 
  private byte[] buf = new byte[1000]; //设置数据包大小,要比发送的数据大
  private DatagramPacket dp =  
    new DatagramPacket(buf, buf.length); //
  private int id; 
 
  public ChatterClient(int identifier) { 
    id = identifier; 
    try { 
      // Auto-assign port number: 
      s = new DatagramSocket(0);//参数不填或是0的话 代表随机选择端口发送
      s.setSoTimeout(10000);//设置超时时间
      hostAddress =  
        InetAddress.getByName("106.13.46.152"); //获得连接端口
    } catch(UnknownHostException e) { 
      System.err.println("Cannot find host"); 
      System.exit(1); 
    } catch(SocketException e) { 
      System.err.println("Can‘t open socket"); 
      e.printStackTrace(); 
      System.exit(1); 
    }  
    System.out.println("ChatterClient starting"); 
  } 
  public void run() { 
    try { 
      for(int i = 0; i < 10; i++) { 
        String outMessage = "Client #" + 
          id + ", message #" + i; 

        // Make and send a datagram: 
        s.send(Dgram.toDatagram(outMessage, 
          hostAddress,  
          ChatterServer.INPORT)); //得到一个DatagramPacket数据包并发送
        // Block until it echoes back: 
        s.receive(dp); //接收数据报
        // Print out the echoed contents: 
        String rcvd = "Client #" + id + 
          ", rcvd from " +  
          dp.getAddress() + ", " +  
          dp.getPort() + ": " + 
          Dgram.toString(dp); 
//        String rcvd = new String(dp.getData(),0,dp.getLength(),"UTF-8");
        System.out.println(dp); 
      } 
    } catch(IOException e) { 
      e.printStackTrace(); 
      System.exit(1); 
    } 
  } 
  public static void main(String[] args) { 
    for(int i = 0; i < 10; i++) 
      new ChatterClient(i).start(); 
  } 
} ///:~