import java.net.*;
import java.io.*;
import java.util.*;
/**
 * <p>Title: 網絡聊天吧</p>
 * <p>Description: 使用數據報創建的聊天服務器</p>
 * <p>Copyright: Copyright (c) 2003</p>
 * <p>Filename: ChatServer.java</p>
 * @author 杜江
 * @version 1.0
 */
public class ChatServer{
 static final int PORT = 4000;//設置服務端口
 private byte[] buf = new byte[1000];
 private DatagramPacket dgp =new  DatagramPacket(buf,buf.length);
 private DatagramSocket sk;
/**
 *<br>方法說明：服務端構造器，實現讀取用戶輸入和通訊
 *<br>輸入參數：
 *<br>返回類型：
 */
 public ChatServer(){
   try{
     //實例化數據報
     sk = new DatagramSocket(PORT);
     System.out.println("Server start.................");
     while(true){
       //等待接收
       sk.receive(dgp);
       //獲取接收信息
       String rcvd = new String(dgp.getData(),0,dgp.getLength())+ 
          ", from address: "+ dgp.getAddress()+
          ", port: "+ dgp.getPort();
       System.out.println(rcvd);
       String outMessage ="";  
        //讀取輸入
         BufferedReader stdin  = new BufferedReader(new InputStreamReader(System.in));
         try{
           outMessage = stdin.readLine();
         }catch(IOException ie){
           System.err.println("IO error!");
         }
       String outString = "Server say: "+ outMessage;
       //拷貝字符到緩存
       byte[] buf = outString.getBytes();
       //打包數據，發送回信息。
       DatagramPacket out = new DatagramPacket(buf,buf.length,dgp.getAddress(),dgp.getPort());
       sk.send(out);
     }
    }catch(SocketException e){
      System.err.println("Can't open socket");
      System.exit(1);
    }catch(IOException e){
     System.err.println("Communication error");
     e.printStackTrace();
     System.exit(1);
    }
 }
 public static void main(String[] args){
   new ChatServer();
 }
}