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);
}
}