datagramserverstring.java~4~

jbuilder2006一书的所有源代码

package datagrams;

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

public class DatagramServerString {

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

class QuoteServerThread extends Thread {

  //创建DatagramSocket类
  protected DatagramSocket datagramSocket = null;
  //创建文件读入类
  protected BufferedReader in = null;
  //标识words文件是否还有语句
  protected boolean moreQuotes = true;

  public QuoteServerThread(String title) throws IOException {
    super(title);
    //为DatagramSocket类创建5555端口
    datagramSocket = new DatagramSocket(5555);

    try {
      //创建文件读入类,读入words.txt文件的内容
      in = new BufferedReader(new FileReader("words.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DatagramSocket接口接收客户端的数据包
        datagramSocket.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
          //使用getNextQuote()方法获取文件的内容
          dString = getNextQuote();
        //将字符串转为Bytes()数组
        buf = dString.getBytes();
        //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
        datagramSocket.send(packet);
      }
      catch (IOException e) {
        e.printStackTrace();
        //当发生异常时,退出发送信息循环
        moreQuotes = false;
      }
    }
    //关闭Datagram接口
    datagramSocket.close();
  }
  //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();
        //退出发送信息的循环
        moreQuotes = false;
        returnValue = "完成信息发送.";
      }
    }
    catch (IOException e) {
      //产生异常时,返回这句话
      returnValue = "产生发送信息错误.";
      e.printStackTrace();
    }
    //返回文件的内容
    return returnValue;
  }
}