java udp 广播

 

 

原文链接: http://blog.csdn.net/yudajun/article/details/8477149

udp 是一种网络通信协议，不需要客户端和服务器端建立连接即可进行通讯功能。相对于Tcp协议它有着tcp用很多优点，例如广播功能。udp的广播功能可以指定特定网段进行广播内容，而无需知道接收者是谁，只有接受者在广播范围内即可接收广播内容。其实基于这个功能可以实现一个局域网群聊室的功能。

udp广播发送有两种形式，

方式一：通过DatagramSocket实现

方式二：通过MulticastSocket 实现

 

方式一：demo;

 

1,数据发送端：

 

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;
import java.net.UnknownHostException;


public class SendIP {

    public static void main(String args[]) {
        new SendIP().lanchApp();
     }

    private void lanchApp(){
        SendThread th=new SendThread();
        th.start();
    }


    private class SendThread extends Thread{
        @Override
        public void run() {
            while(true){
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                try {
                    BroadcastIP();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }

        private void BroadcastIP()throws Exception{
             DatagramSocket dgSocket=new DatagramSocket();
              byte b[]="你好，这是我发给你的消息".getBytes();
              DatagramPacket dgPacket=new DatagramPacket(b,b.length,InetAddress.getByName("255.255.255.255"),8989);
              dgSocket.send(dgPacket);
              dgSocket.close();
              System.out.println("send message is ok.");
        }
    }

}

2，数据接收端：

 

 

import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

    public class SearchIP{

         public static void main(String args[])throws Exception{

             new SearchIP().lanchApp();
         }

         private void lanchApp(){
             receiveThread th=new receiveThread();
                th.start();
            }

         private class receiveThread extends Thread{
             @Override
                public void run() {
                    while(true){
                        try {
                            Thread.sleep(1000);
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                        try {
                            receiveIP();
                        } catch (Exception e) {
                            e.printStackTrace();
                        }
                    }
             }

            private void receiveIP() throws Exception{
                 DatagramSocket dgSocket=new DatagramSocket(8989);
                  byte[] by=new byte[1024];
                  DatagramPacket packet=new DatagramPacket(by,by.length);
                  dgSocket.receive(packet);

                  String str=new String(packet.getData(),0,packet.getLength());

                  System.out.println("接收到数据大小:"+str.length());
                  System.out.println("接收到的数据为："+str);
                  dgSocket.close();
                  System.out.println("recevied message is ok.");
             }
         }


    }

 

方式二demo;

 

1,数据发送端：

 

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.InetAddress;
import java.net.MulticastSocket;


public class MulBroadcast extends Thread{

    String info ="节目预告： 恭喜您中500w彩票了";
    int port =9898;
    InetAddress address;
    MulticastSocket socket;

   public MulBroadcast(){
       try{
       address=InetAddress.getByName("233.0.0.0");
       socket=new MulticastSocket(port);
       socket.setTimeToLive(1);
       socket.joinGroup(address);
       }catch(IOException e){
           e.printStackTrace();
       }
    }

    @Override   //最简单的方法也就是建立一个线程来运行
    public void run(){
        while(true){
            byte[] data=info.getBytes();
            DatagramPacket packet=new DatagramPacket(data,data.length,address,port);

            try {
                socket.send(packet);
                Thread.sleep(3000);
            } catch (Exception e) {
                e.printStackTrace();
            }
            System.out.println("消息已发送：");
        }
    }

    public static void main(String[] args){
        new MulBroadcast().start();
    }

}

2，数据接收端：

 

 

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.InetAddress;
import java.net.MulticastSocket;


public class MulReceiverIP extends Thread{

        int port=9898;
        InetAddress group;
        MulticastSocket socket; //socket sends and receives the packet.
        DatagramPacket packet;
        byte[] buf=new byte[30];// If the message is longer than the packet's length, the message is truncated.

    public MulReceiverIP(){
         try {
                socket=new MulticastSocket(port);

                group=InetAddress.getByName("233.0.0.0");
                socket.joinGroup(group);    //加入广播组,加入group后,socket发送的数据报,可以被加入到group中的成员接收到。
                packet=new DatagramPacket(buf,buf.length);

            } catch (IOException e) {
                e.printStackTrace();
            }
    }

      @Override
        public void run(){
            while(true){
                try {
                    socket.receive(packet);
                } catch (IOException e) {
                    e.printStackTrace();
                }
                //      String message=new String(buf);
               String message=new String(packet.getData(),0,packet.getLength());//very important !!
               System.out.println("接受消息内容: "+message);

            }
        }

      public static void main(String[] args) {
            new MulReceiverIP().start();
    }

}