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 testdual() {

  }

  public void init() {
    super.init();
    imageshow is = new imageshow();
    is.adddataswaplistener(this);
    thread thread = new thread(is, "test");
    thread.start();
  }

  public static void main(string[] args) {
    testdual test = new testdual();
    test.initmain();
    test.go();
    datagramrecvsender_s dgrs = new datagramrecvsender_s();
    dgrs.adddataswaplistener(test);
    thread thread = new thread(dgrs, "test");
    thread.start();
  }

  public void initmain() {
    super.initmain();
    ip = new jimagepanel();
    root.setlayout(new borderlayout(5, 5));
    root.add(ip, borderlayout.center);
  }

  public void ondatasendfinished(object s, dataswapevent e) {

  }

  public void ondatarecvfinished(object s, dataswapevent e) {
    this.bi = e.getimage();
    ip.setimage(bi);
    system.out.println("recv finished!");
  }
}

testdual扩展的dualwindow类清单:

package recmail.multiservice;

import javax.swing.jpanel;
import javax.swing.jframe;
import javax.swing.japplet;

public class dualwindow
    extends japplet {
  protected jpanel root;
  private jframe frame;
  public dualwindow() {
  }

  public void init() {
    root = new jpanel();
    this.setcontentpane(root);
  }

  public void initmain() {
    root = new jpanel();
  }

  public static void main(string[] args) {
    testdual test = new testdual();
    test.initmain();
    test.start();
    test.go();
  }

  public void go() {
    frame = new jframe();
    frame.setcontentpane(root);
    frame.setdefaultcloseoperation(jframe.exit_on_close);
    frame.setsize(300, 200);
    frame.validate();
    frame.setvisible(true);
  }
}


下一篇介绍广播的实现.