downloadingfileserver.java

下载文件服务器说明(使用Socket完成文件的下载的任务

/**
 * 下载文件服务器
 * */

package downloadingfile;

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

public class DownloadingFileServer
{
  //声明所需的类的变量
  //声明ServerSocket以及Socket
  private ServerSocket SSocket = null;
  private Socket socket = null;

  //读取客户端提交的请求文件名字的流类
  BufferedReader BRClient = null;
  //指向客户端的输出流
  BufferedOutputStream BOSClient = null;
  //指向服务器文件的本地流
  BufferedInputStream BISServer = null;

  public void Service()
  {
    try
    {
      SSocket = new ServerSocket(8000);
      System.out.println("等待客户端连接...");
      socket = SSocket.accept();
      System.out.println("客户端已经连接...");

      //指向客户端的输入流用来读取客户端提交的文件名
      BRClient = new BufferedReader(new InputStreamReader(socket.getInputStream()));
      //指向客户端的输出流(注意流链的写法)
      BOSClient = new BufferedOutputStream(socket.getOutputStream());
      //读取客户端所需的文件的名字
      String fileName = BRClient.readLine();
      //指向服务器本地的文件名，此时文件如果不存在则抛出异常。
      BISServer = new BufferedInputStream(new FileInputStream(fileName));
      //如果文件存在向客户端给出准备完成的信号
      BOSClient.write("000".getBytes());
      BOSClient.flush();

      //读取文件的内容发送给客户端
      byte[] byte1 = new byte[8192];
      int count1 = 0;
      while ( (count1 = BISServer.read(byte1, 0, byte1.length)) > -1)
      {
        BOSClient.write(byte1, 0, count1);
        BOSClient.flush();
      }
    }

    catch (java.io.FileNotFoundException e)
    {
      try
      {
        //如果文件不存在给出文件不存在的信号
        BOSClient.write("404".getBytes());
        BOSClient.flush();
      }
      catch (IOException IOE)
      {
        IOE.printStackTrace();
      }
    }
    catch (Exception exception)
    {
      exception.printStackTrace();
    }
    finally
    {
      try
      {
        if (BRClient != null)
        {
          BRClient.close();
        }
        if (BOSClient != null)
        {
          BOSClient.close();
        }
        if (BISServer != null)
        {
          BISServer.close();
        }
        if (socket != null)
        {
          socket.close();
        }
        if (SSocket != null)
        {
          SSocket.close();
        }
      }
      catch (Exception exception)
      {
        exception.printStackTrace();
      }
    }
  }

  public static void main(String[] args)
  {
    DownloadingFileServer DFServer = new DownloadingFileServer();
    DFServer.Service();
  }
}