Question

我在使用Java实现Active ftp服务器时遇到问题。

我需要一台将文件发送到客户端的服务器。等待客户端发送回响应文件。（这是一个主从协议。客户端只有在收到带有命令的文件后才进行处理。）

运行代码时，得到的文件为空。

我的服务器代码。

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.io.BufferedOutputStream;
import java.io.FileOutputStream;
import java.io.InputStream;

public class ftps {
  public final static int FILE_SIZE=6022386;
  public final static int SOCKET_PORT = 18901;  // you may change this
  public final static String FILE_TO_SEND = "c:/workspace/test/sentfromserver.txt";  // you may change this
  public final static String FILE_TO_RECEIVED="c:/workspace/test/gotfromclient.txt";
  public static void main (String [] args ) throws IOException {
    FileInputStream fis = null;
    BufferedInputStream bis = null;
    OutputStream os = null;
    ServerSocket servsock = null;
    FileOutputStream fos = null;
    BufferedOutputStream bos = null;
    Socket sock = null;
    int bytesRead;
    int current;
    try {
      servsock = new ServerSocket(18901);
      while (true) {
        System.out.println("Waiting...");
        try {
          sock = servsock.accept();
          System.out.println("Accepted connection : " + sock);
          // send file
          File myFile = new File (FILE_TO_SEND);
          byte [] mybytearray  = new byte [(int)myFile.length()];
          fis = new FileInputStream(myFile);
          bis = new BufferedInputStream(fis);
          bis.read(mybytearray,0,mybytearray.length);
          os = sock.getOutputStream();
          System.out.println("Sending " + FILE_TO_SEND + "(" + mybytearray.length + " bytes)");
          os.write(mybytearray,0,mybytearray.length);
          os.flush();
          System.out.println("Done.");
          mybytearray  = new byte [FILE_SIZE];
          InputStream is = sock.getInputStream();
          fos = new FileOutputStream(FILE_TO_RECEIVED);
          bos = new BufferedOutputStream(fos);
          bytesRead = is.read(mybytearray,0,mybytearray.length);
          current = bytesRead;

          do {
             bytesRead =
                is.read(mybytearray, current, (mybytearray.length-current));
             if(bytesRead >= 0) current += bytesRead;
          } while(bytesRead > -1);

          bos.write(mybytearray, 0 , current);
          bos.flush();
          System.out.println("File " + FILE_TO_RECEIVED
              + " downloaded (" + current + " bytes read)");
        }
        finally {
          if (bis != null) bis.close();
          if (os != null) os.close();
          if (sock!=null) sock.close();
          if (bos!=null) bos.close();
        }
      }
    }
    finally {
      if (servsock != null) servsock.close();
    }
  }
}

客户端

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.net.Socket;
import java.io.BufferedOutputStream;
import java.io.FileOutputStream;
import java.io.InputStream;

public class ftpcc {

     public final static int SOCKET_PORT = 18901;      // you may change this
      public final static String SERVER = "127.0.0.1";  // localhost
      public final static String
           FILE_TO_RECEIVED = "c:/workspace/test/gotfromserver.txt";  // you may change this, I give a
                                                                // different name because i don't want to
                                                                // overwrite the one used by server...
      public final static String FILE_TO_SEND="c:/workspace/test/sentfromclient.txt";
      public final static int FILE_SIZE = 6022386; // file size temporary hard coded
                                                   // should bigger than the file to be downloaded

      public static void main (String [] args ) throws IOException {
        int bytesRead;
        int current = 0;
        FileOutputStream fos = null;
        BufferedOutputStream bos = null;
        FileInputStream fis = null;
        BufferedInputStream bis = null;
        OutputStream os = null;
        Socket sock = null;
        try {
          sock = new Socket(SERVER, 18901);
          System.out.println("Connecting...");

          // receive file
          byte [] mybytearray  = new byte [FILE_SIZE];
          InputStream is = sock.getInputStream();
          fos = new FileOutputStream(FILE_TO_RECEIVED);
          bos = new BufferedOutputStream(fos);
          bytesRead = is.read(mybytearray,0,mybytearray.length);
          current = bytesRead;

          do {
             bytesRead =
                is.read(mybytearray, current, (mybytearray.length-current));
             if(bytesRead >= 0) current += bytesRead;
          } while(bytesRead > -1);

          bos.write(mybytearray, 0 , current);
          bos.flush();
          System.out.println("File " + FILE_TO_RECEIVED
              + " downloaded (" + current + " bytes read)");
          File myFile = new File (FILE_TO_SEND);
          mybytearray  = new byte [(int)myFile.length()];
          fis = new FileInputStream(myFile);
          bis = new BufferedInputStream(fis);
          bis.read(mybytearray,0,mybytearray.length);
          os = sock.getOutputStream();
          System.out.println("Sending " + FILE_TO_SEND + "(" + mybytearray.length + " bytes)");
          os.write(mybytearray,0,mybytearray.length);
          os.flush();
          System.out.println("Done.");
        }
        finally {
          if (fos != null) fos.close();
          if (bos != null) bos.close();
          if (sock != null) sock.close();
          if (bis !=null) bis.close();
        }
      }

    }

Answer 1

InputStream.read(byte[], int, int)方法在返回任何内容之前等待输入，并且您已经在循环之前读取了整个文件，因此服务器和客户端都陷入了do..while循环中。删除那些，您的代码将正常工作。

编辑：选中此question，了解如何使用循环读取文件的详细信息。

我在实施“活动FTP服务器”时遇到问题

1 个答案: