datagramsserver.java

JAVA类库参考手册

import java.io.*;
import java.net.*;
import java.util.*;

public class DatagramsServer {
  public static void main(String[] args) throws IOException {
    new QuoteServerThread("SingleServerThread").start();
  }
}

class QuoteServerThread extends Thread {

  protected DatagramSocket socket = null;  //创建DatagramSocket类
  protected BufferedReader in = null;      //创建文件写入类
  protected boolean moreQuotes = true;     //标识listwords文件是否还有语句

  public QuoteServerThread(String title) throws IOException {
    super(title);
    socket = new DatagramSocket(8888);  //为DatagramSocket类创建8888端口

    try {
      //创建文件读入类,读入listwords.txt文件的内容
      in = new BufferedReader(new FileReader("listwords.txt"));
    } catch (FileNotFoundException e) {
      System.err.println("不能打开文件");
    }
  }


  public void run() {

    while (moreQuotes) {
      try {
        byte[] buf = new byte[200];

        //使用byte数组创建数据包
        DatagramPacket packet = new DatagramPacket(buf, buf.length);
        //使用socket接口接收客户端的数据包
        socket.receive(packet);

        //创建dString字符串读取文件的内容
        String dString = null;
        if (in == null)
          dString = new Date().toString();
        else
          dString = getNextQuote();  //使用getNextQuote()方法获取文件的内容
        buf = dString.getBytes();    //将字符串转为Bytes()数组

        //根据接收的数据包获取网络地址与端口
        InetAddress address = packet.getAddress();
        int port = packet.getPort();
        //重新创建带有网络地址与端口的数据包
        packet = new DatagramPacket(buf, buf.length, address, port);
        //根据数据包的地址与端口发送数据包
        socket.send(packet);
      } catch (IOException e) {
        e.printStackTrace();
        moreQuotes = false;   //当发生异常时,退出发送信息循环
      }
    }
    socket.close();  //关闭Datagram接口
  }

  //读取文件内容的方法
  protected String getNextQuote() {
    String returnValue = null;
    try {
      //读入文件内容
      if ((returnValue = in.readLine()) == null) {
        //如果到了文件的结尾,返回下面的语句
        in.close();
        moreQuotes = false;               //退出发送信息的循环
        returnValue = "不要泄气,继续努力.";
      }
    } catch (IOException e) {
      returnValue = "在服务端有错误产生.";   //产生异常时,返回这句话
    }
    return returnValue;
  }
}