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Java数据报编程之单播

答案: 

实际上,单播就是一个报文从源主机向另一个目标主机发送,接收目标只有一个.

首先,写收发器类DatagramRecvSender_s,这个类既要发送数据报又要接收数据报,发送一个文件夹中的所有图片,一张一张的进行,接收是在一个线程中进行,每收完一个文件,就激活一个事件,事件处理器处理这个事件.

类清单为:

package recmail.multiservice;

import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;
import java.net.SocketAddress;
import java.net.UnknownHostException;
import java.net.InetSocketAddress;
import java.io.IOException;
import java.util.ArrayList;
import java.net.InetAddress;
import java.io.File;
import java.util.Iterator;

public class DatagramRecvSender_s extends DataSwapListenerAdapter
    implements Runnable {
  public static final int DatagramPort = 10698;
  private java.net.DatagramSocket road;
  private InetAddress ia;
  DatagramPacket dp;
  public static final int Datagram_Length = 8192;
  private DataPacket cdp;
  private boolean ishandling = true;

  DataSwapEvent dsevent;
  /**
   * 这个构造器用于接收数据报.
   */
  public DatagramRecvSender_s() {
    try {
      System.out.println("recv ...");
      ia = InetAddress.getByName("localhost");//192.168.0.17"127.0.0.1"
      dsevent = new DataSwapEvent(this);
      SocketAddress sa = new InetSocketAddress(ia,
                                               DatagramRecvSender_s.DatagramPort);
      //至少要指定数据报接收端口,这是对接收端的唯一要求.当然如果主机是多址主机,需要road = new DatagramSocket(sa);
      road = new DatagramSocket(DatagramRecvSender_s.DatagramPort);
      System.out.println(road.isBound()+"::"+road.getBroadcast());
    }
    catch (SocketException ex) {
      ex.printStackTrace();
    }
    catch (Exception ex1) {
      ex1.printStackTrace();
    }
  }
  /**
   * 这个构造器用于发送数据报.
   * @param send String
   */
  public DatagramRecvSender_s(String send) {
    try {
      System.out.println("start sending ...");
      ia = InetAddress.getByName("192.168.0.4");//"255.255.255.255""192.168.0.4""127.0.0.1"
      dsevent = new DataSwapEvent(this);
      SocketAddress sa = new InetSocketAddress(ia,
                                               DatagramRecvSender_s.DatagramPort);
      //如果需要接收数据报,就需要指定一个端口,否则不必指定.road = new DatagramSocket(DatagramRecvSender_s.DatagramPort-1);
      road = new DatagramSocket();
      System.out.println("isBound--"+road.isBound()+":getBroadcast--"+road.getBroadcast());
    }
    catch (SocketException ex) {
      ex.printStackTrace();
    }
    catch (UnknownHostException ex1) {
      ex1.printStackTrace();
    }
  }

  public void sendFile(String file) {
    cdp = new DataPacket(file);
    System.out.println(file);
    Iterator it = cdp.getDataPackets().iterator();
    byte[] b;
    while (it.hasNext()) {
      b = ( (DataEntry) it.next()).getByte();
      //数据报是自包含的,自描述的数据,它的投递是由路由器执行的,路由器路由算法根据报文的目标地址选择适当的路由递送报文,
      //所以数据报中要指定目标IP地址和目标主机处理端口.
      DatagramPacket dp = new DatagramPacket(b, 0, b.length, ia,DatagramRecvSender_s.DatagramPort);
      try {
        Thread.sleep(100);
        if(dp==null)
          continue;
        road.send(dp);
      }
      catch (Exception ex) {
        ex.printStackTrace();
      }
    }
  }

  public boolean isHandling() {
    return ishandling;
  }

  public void isHandling(boolean ishand) {
    ishandling = ishand;
  }

  public void run() {
    byte[] buffer = new byte[DataPacket.DataSwapSize];
    DatagramPacket packet = new DatagramPacket(buffer, buffer.length);
    DataPacket dp = new DataPacket();
    while (ishandling) {
      packet.setLength(buffer.length);
      System.out.println("wait .. ");
      try {
        road.receive(packet);
        dp.Add(packet.getData());
        if (dp.isFull()) {
          dsevent.setImage(dp.Gereratedata());
          this.processRecvFinishedEvent(dsevent);
          dp = new DataPacket();
        }
      }
      catch (IOException ex) {
        System.out.println(ex);
      }
    }
  }

  public static void main(String[] args) {
    String file[];
    ArrayList al = new ArrayList();
    String path = "E:\\nature\\";
    File f = new File(path);
    file = f.list();
    DatagramRecvSender_s dgrs = new DatagramRecvSender_s("");
    for(int j=0;j<1000;j++)
    for (int i = 0; i < file.length; i++) {
      try {
        Thread.sleep(2000);
      }
      catch (InterruptedException ex) {
      }
      if (file[i].endsWith("jpg") || file[i].endsWith("bmp"))
        dgrs.sendFile(path + file[i]);
    }
  }
}

下面看接收端的界面.

package recmail.multiservice;

import java.awt.BorderLayout;

public class testDual
    extends DualWindow implements DataSwapListener {
  JImagePanel ip;
  java.awt.Image bi;

  public testD

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