Java数据报编程之单播[1]

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();
    }
  }