Java資料報編程之廣播

編程|資料  

UDP廣播,實際上是很簡單的,理解IP編址方案,就理解什麼是廣播,很多文章稱為多播,我認為稱為廣播比較好,因為多播是對廣播和組播的泛指,在Java程式中處理自然是不同的了,本文和下一篇只為強調概念.

正如前面所說,廣播位址包括定向廣播位址和有限廣播位址,TCP/IP協議規定,這兩種地址只能在本網中出現,路由器執行了這個規定,不把目標地址為廣播位址的報文轉寄到其它網路,而組播就不同,下一篇介紹組播編程.

這個廣播的程式可以簡單的通過修改單播程式中的報文的目標地址成廣播位址即可成為廣播程式.

package recmail.multiservice;

import java.net.DatagramSocket;
import java.net.*;
import java.io.*;
import java.util.ArrayList;
import java.util.Iterator;

public class DatagramRecvSender_b 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;
  /**
   * 這個構造器用於接收資料報.
   */
  public DatagramRecvSender_b() {
    try {
      System.out.println("recv ...");
      dsevent = new DataSwapEvent(this);
      SocketAddress sa = new InetSocketAddress(
                                               DatagramRecvSender_b.DatagramPort);
      //至少要指定資料報接收埠,這是對接收端的唯一要求.當然如果主機是多址主機,需要road = new DatagramSocket(sa);
      road = new DatagramSocket(DatagramRecvSender_b.DatagramPort);
      System.out.println(road.isBound()+"::"+road.getBroadcast());
    }
    catch (SocketException ex) {
      ex.printStackTrace();
    }
    catch (Exception ex1) {
      ex1.printStackTrace();
    }
  }
  /**
   * 這個構造器用於發送資料報.
   * @param send String
   */
  public DatagramRecvSender_b(String send) {
    try {
      System.out.println("send ...");
      //這個類可以計算本地網的定向廣播位址.
      BroadcastAddr info = new BroadcastAddr();
      info.setNetmask("255.255.255.0");
      info.setNetaddr("192.168.0.106");
      info.execCalc();
      ia = InetAddress.getByName(info.getNetbroadcastaddr());//"255.255.255.255"
      dsevent = new DataSwapEvent(this);
      SocketAddress sa = new InetSocketAddress(ia,
                                               DatagramRecvSender_b.DatagramPort);
      //如果需要接收資料報,就需要指定一個連接埠,否則不必指定.road = new DatagramSocket(DatagramRecvSender_s.DatagramPort-1);
      road = new DatagramSocket();
      //DatagramSocket類執行個體的getBroadcast()返回true,即該類的廣播屬性預設設定是true,就是使能的.
      //road.setBroadcast(true);可以測試一下 當執行了road.setBroadcast(false)後會出現什麼狀況.
      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();
      DatagramPacket dp = new DatagramPacket(b, 0, b.length, ia,DatagramRecvSender_b.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();
    //換成你機器上的圖象檔案夾
    String path = "E:\\nature\\";
    File f = new File(path);
    file = f.list();
    DatagramRecvSender_b dgrs = new DatagramRecvSender_b("");
    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]);
    }
  }
}

  public static void main(String[] args) {
    String file[];
    ArrayList al = new ArrayList();
    String path = "E:\\nature\\"; //nature mzip
    File f = new File(path);
    file = f.list();
    DatagramRecvSender_b dgrs = new DatagramRecvSender_b("");
    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"))
        //System.out.println(file[i]);
        //al.add(path + file[i]);
        dgrs.sendFile(path + file[i]);
    }
  }
}

接收端顯示介面和單播相同,修要修改的只有一句:

在類testDual的main方法中,把DatagramRecvSender_s改為DatagramRecvSender_b即可,把接收端放到你的區域網路上的幾個機器上同時運行,你應該會看到不斷顯示的圖象.

  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();
  }

下一篇介紹組播編程.