package udp;

import java.net.InetAddress;

public class data {
 InetAddress Address;
 int Port;
 public InetAddress getAddress() {
  return Address;
 }
 public void setAddress(InetAddress address) {
  Address = address;
 }
 public int getPort() {
  return Port;
 }
 public void setPort(int port) {
  Port = port;
 }
}

package udp;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;
import java.util.ArrayList;

public class Server {
 DatagramSocket socket = null; 
 ArrayList<data> client;
 
 public Server() { 
  try {
   socket = new DatagramSocket(8888);
  } catch (SocketException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }
  client = new ArrayList<data>();
 }
 
 public void s_r(){
  try {
   
   while(true) {
    byte[] buf = new byte[3000];
    //接收数据的数据包
    DatagramPacket packet = new DatagramPacket(buf,buf.length);
    socket.receive(packet);
    //地址
    InetAddress clientAddress = packet.getAddress();
    //端口号    
    int clientPort = packet.getPort();
    data d = new data();
    d.setAddress(clientAddress);
    d.setPort(clientPort);
    int i=0;
    //判断客户端集合里是否存在发送新消息的客户端
    for(;i<client.size();i++) {
     if(client.get(i).getAddress().equals(clientAddress)&&client.get(i).getPort()==clientPort) {
      break;
     }
    }
    if(i==client.size()) {
     client.add(d);
    }
    String s=new String(packet.getData()).trim()+"来自:"+clientAddress.getHostAddress()+":"+clientPort;
    System.out.println(s);
    //把信息发给每个客户端
    for(data c:client) {
     try {
      //地址
      InetAddress cAddress = c.getAddress();
      //端口号
      int cPort = c.getPort();
      
      buf = s.getBytes();
      //创建要发送的数据包
      packet = new DatagramPacket(buf,buf.length,cAddress,cPort);
      socket.send(packet);
      } catch (IOException e) {
       // TODO Auto-generated catch block
       e.printStackTrace();
      }
     }    
   }
  } catch (SocketException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  } catch (IOException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }finally {
   if(socket!=null)socket.close();
  }
  
 }  
 public static void main(String[] args) {
  Server s = new Server();
  s.s_r();
 }
}

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

public class Client {
 DatagramSocket socket = null;
 DatagramPacket packet;
 InetAddress address = null;
 Client(){
  try {
   socket = new DatagramSocket();
  } catch (SocketException e) {
   // TODO Auto-generated catch block
   e.printStackTrace();
  }  
 }
 
 public void s_r() {
  try {
   // 把表示服务器端IP地址的字符串转换成InetAddress对象
   address = InetAddress.getByName("127.0.0.1");
   } catch (UnknownHostException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
  }  
  String s = "登陆";
  byte[] b = s.getBytes();
  packet = new DatagramPacket(b,b.length,address,8888);
  try {
   socket.send(packet);
  } catch (IOException e1) {
   // TODO Auto-generated catch block
   e1.printStackTrace();
  }

  //发送消息的线程
   new Thread(new Runnable() {
    @Override
    public void run() {
     // TODO Auto-generated method stub
     String sendStr;
     BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));
     try {
      while((sendStr = stdIn.readLine())!=null) {
       byte[] buf = sendStr.getBytes();
       packet = new DatagramPacket(buf,buf.length,address,8888);
       socket.send(packet);
      }
     } catch (IOException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
     }     
    }
    
   }).start();

   //接收消息的线程
   new Thread(new Runnable() {

    @Override
    public void run() {
     // TODO Auto-generated method stub
     byte[] buf_1 = new byte[3000];
     // 使用空字节数组构造空数据包
     DatagramPacket packet = new DatagramPacket(buf_1,buf_1.length);
     try {
       while(true) {
        socket.receive(packet);
        String received = new String(packet.getData(),0,packet.getLength()).trim();
        System.out.println("接收到的信息:"+received); 
       }
          
     } catch (IOException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
     }
    }
   }).start();
 }
 
 public static void main(String[] args) {
  Client c = new Client();
  c.s_r();
 } 
}