Question

我有一个FileServer和一个FileClient，服务器在客户端连接时发送文件。这是一个简单的程序，只是为了理解背后的概念。

我能够将文件从Server发送到Client，缓冲区为1024。问题是收到的文件总是比原始文件少大约0.01 MB。因此mp3文件会丢失一些信息，而视频文件则无法播放。

我在服务器和放大器的while循环中放了一些prinln语句。客户。我发现我的服务器没有发送整个文件。

  //Server
  byte [] mybytearray  = new byte [1024];    
  FileInputStream fis = new FileInputStream(myFile);
  BufferedInputStream bis = new BufferedInputStream(fis);
  bis.read(mybytearray,0,mybytearray.length);
  OutputStream os = sock.getOutputStream();
  System.out.println("Sending...\n mybytearray length:"+mybytearray.length+"file   length:"+(int)myFile.length());
  int read, readTotal=0;
  while ((read = fis.read(mybytearray,0,mybytearray.length)) != -1) { 

      os.write(mybytearray, 0, read);
      System.out.println("File REad:"+read+"readtotal:"+readTotal); //*
      readTotal += read;
}
  System.out.println("Final File Read:"+read+" Final readtotal:"+readTotal);
  os.flush();
  sock.close();
  }

Println语句输出为：

Sending...
mybytearray length:1024file length:12767554
File REad:1024readtotal:0
File REad:1024readtotal:1024
.............and a lot of it...and then
File REad:1024readtotal:12756992
File REad:1024readtotal:12758016
File REad:322readtotal:12759040
Final File Read:-1 Final readtotal:12759362

文件长度：12767554＆amp;最后阅读总数：12759362 shud相等。我不明白为什么最后一个读数值较低[322]，而它仍然可以有1024。

任何形式的帮助都值得赞赏。感谢。

[编辑]

//Client
int read;
int totalRead = 0;

while ((read = is.read(mybytearray,0,mybytearray.length)) != -1) {
        bos.write(mybytearray, 0 , read);

        totalRead += read;
        System.out.println("\nread:"+read+"\ntotalread: "+totalRead);
}
System.out.println("Final File Read:"+read+" Final readtotal:"+totalRead);
bos.write(mybytearray, 0 , read);  //57 Line in FileClient.java
bos.flush();

我再次尝试发送文件。这次是一个txt。这是我服务器的输出

Sending...
mybytearray length:1024file length:1232
File REad:1024readtotal:0
File REad:208readtotal:1024
Final File Read:-1 Final readtotal:1232

和客户端上的这个

read:208
totalread: 1232
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException
   Final File Read:-1     Final readtotal:1232

at java.lang.System.arraycopy(Native Method)
at java.io.BufferedOutputStream.write(Unknown Source)
at FileClient.main(FileClient.java:57)

readtotal值相同，但有时我会收到此错误，有时我不会。

[大编辑 - 完整的客户代码]

public class FileClient{
 public static void main (String [] args ) throws IOException {

long start = System.currentTimeMillis();
int bytesRead;
int current = 0;
final JFrame f = new JFrame("Sample");
f.getContentPane().setLayout(new FlowLayout());
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setSize(590,490);
f.setVisible(true);
// localhost for testing
Socket sock = new Socket("localhost",13267);
System.out.println("Connecting...");
File f1=new File(RecieveObject(sock));


// receive file
byte [] mybytearray  = new byte [1024];
InputStream is = sock.getInputStream();


FileOutputStream fos = new FileOutputStream(f1);
ProgressMonitorInputStream nn= new ProgressMonitorInputStream(f,"reading",is);
BufferedOutputStream bos = new BufferedOutputStream(fos);
 /*   bytesRead = is.read(mybytearray,0,mybytearray.length);
current = bytesRead;


do {
   bytesRead =
      is.read(mybytearray, current, (mybytearray.length-current));
   System.out.println("mybytesarray length: "+mybytearray.length+"\ncurrent:"+current+"\nbytesread: "+bytesRead);
   if(bytesRead >= 0) current += bytesRead;
} while(bytesRead > -1);

bos.write(mybytearray, 0 , current);
bos.flush();
 */
int read;
int totalRead = 0;
//InputStream clientInputStream = clientSocket.getInputStream();
while ((read = is.read(mybytearray,0,mybytearray.length)) != -1) {
        bos.write(mybytearray, 0 , read);

        totalRead += read;
        System.out.println("\nread:"+read+"\ntotalread: "+totalRead);
}
System.out.println("Final File Read:"+read+" Final readtotal:"+totalRead);
 //   bos.write(mybytearray, 0 , read);
bos.flush();
long end = System.currentTimeMillis();
System.out.println(end-start);
bos.close();
sock.close();

}
public static  String RecieveObject(Socket s) {
    String str = null;
    try{
    ObjectInputStream is = new ObjectInputStream(s.getInputStream());



            str =(String)is.readUTF();


    }
    catch(IOException ex){}
    return str;
}

}

Answer 1

由于您的第5行（包括评论），您错过了文件的开头（最多1024个字节）。您从输入中读取并将其提前，而不将其发送到客户端。删除它：

bis.read(mybytearray,0,mybytearray.length);

此外，您没有在循环中使用BufferedInputStream。在这里使用bis.read代替fis.read（如果您仍想要缓冲读取） - 或者一起删除BufferedInputStream。

你的另一个问题是你正在读取客户端上的最后一个字节，然后再次进入循环。再次调用is.read。而不是返回-1，它正在抛出IOException，因为套接字的另一侧已经关闭。因此，不会调用bos.flush（）和bos.close（），并且您的最终字节永远不会写入磁盘。要解决此问题，请在关闭之前尝试致电sock.shutdownOutput。无论如何，你都希望在此周围添加一些适当的异常处理。

Answer 2

byte [] mybytearray  = new byte [1024];    
FileInputStream fis = new FileInputStream(myFile);
BufferedInputStream bis = new BufferedInputStream(fis);
OutputStream os = sock.getOutputStream();
System.out.println("Sending...\n mybytearray length:"+mybytearray.length+"filelength:"+(int)myFile.length());
int read, readTotal=0;
while ((read = bis.read(mybytearray,0,mybytearray.length)) != -1) { 
    os.write(mybytearray, 0, read);
    System.out.println("File REad:"+read+"readtotal:"+readTotal); //*
    readTotal += read;
}
System.out.println("Final File Read:"+read+" Final readtotal:"+readTotal);
os.flush();
sock.close();
}

文件传输中的数据丢失 - JAVA？

2 个答案: