Question

我编写了一个用于传输小文件的小型客户端 - 服务器代码。它使用数据输出流和数据输入流的readFully（）方法。出于显而易见的原因，此代码不适用于较大的文件。在将大文件发送到客户端之前，我想将大文件分割成每个1Kb的较小块。但我想不出任何解决方案（比如如何在数据输出流上写多个块以及正确的偏移量以及如何在接收端重新组装它们。任何人都可以提供解决方法吗？如果你可以修改我的代码会非常有用：

发件人（服务器）：

public void sendFileDOS() throws FileNotFoundException {
    runOnUiThread( new Runnable() {
          @Override
          public void run() {
              registerLog("Sending. . . Please wait. . .");
          }
        });
    final long startTime = System.currentTimeMillis();
    final File myFile= new File(filePath); //sdcard/DCIM.JPG
    byte[] mybytearray = new byte[(int) myFile.length()];
    FileInputStream fis = new FileInputStream(myFile);  
    BufferedInputStream bis = new BufferedInputStream(fis);
    DataInputStream dis = new DataInputStream(bis);
    try {
        dis.readFully(mybytearray, 0, mybytearray.length);
        OutputStream os = socket.getOutputStream();
        //Sending file name and file size to the client  
        DataOutputStream dos = new DataOutputStream(os);     
        dos.writeUTF(myFile.getName());     
        dos.writeLong(mybytearray.length);     
        int i = 0;
        final ProgressBar myProgBar=(ProgressBar)findViewById(R.id.progress_bar);
        while (i<100) {
            dos.write(mybytearray, i*(mybytearray.length/100), mybytearray.length/100);
            final int c=i;
            runOnUiThread( new Runnable() {
                  @Override
                  public void run() {
                      myProgBar.setVisibility(View.VISIBLE);
                      registerLog("Completed: "+c+"%");
                      myProgBar.setProgress(c);
                      if (c==99)
                          myProgBar.setVisibility(View.INVISIBLE);
                  }
                });
            i++;
        }    
        dos.flush();

    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    runOnUiThread( new Runnable() {
          @Override
          public void run() {
              long estimatedTime = (System.currentTimeMillis() - startTime)/1000;
              registerLog("File successfully sent");
              registerLog("File size: "+myFile.length()/1000+" KBytes");
              registerLog("Elapsed time: "+estimatedTime+" sec. (approx)");
              registerLog("Server stopped. Please restart for another session.");
              final Button startServerButton=(Button)findViewById(R.id.button1);
              startServerButton.setText("Restart file server");
          }
        });
}

接收人（客户）：

public class myFileClient {
final static String servAdd="10.141.21.145";
static String filename=null;
static Socket socket = null;
static Boolean flag=true;

/**
 * @param args
 */
public static void main(String[] args) throws IOException {
    // TODO Auto-generated method stub
    initializeClient();
    receiveDOS();      
}
public static void initializeClient () throws IOException {
    InetAddress serverIP=InetAddress.getByName(servAdd);
    socket=new Socket(serverIP, 4444);
}
public static void receiveDOS() {
    int bytesRead;
    InputStream in;
    int bufferSize=0;

    try {
        bufferSize=socket.getReceiveBufferSize();
        in=socket.getInputStream();
        DataInputStream clientData = new DataInputStream(in);
        String fileName = clientData.readUTF();
        System.out.println(fileName);
        OutputStream output = new FileOutputStream("//home//evinish//Documents//Android//Received files//"+ fileName);
        long size = clientData.readLong();
        byte[] buffer = new byte[bufferSize];
        while (size > 0
                && (bytesRead = clientData.read(buffer, 0,
                        (int) Math.min(buffer.length, size))) != -1) {
            output.write(buffer, 0, bytesRead);
            size -= bytesRead;
        }

    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

请帮忙！提前致谢！：）

Answer 1

你是对的，这是一种糟糕的方式。它浪费了记忆和时间;它假定文件大小是32位;它假定整个文件适合内存;它假定在一次读取中读取整个文件;并且在读完整个文件之前它不会发送任何内容。

在Java中复制流的规范方法是：

while ((count = in.read(buffer)) > 0)
{
  out.write(buffer, 0, count);
}

它适用于您喜欢的任何大小的缓冲区，因此您可以使用任何大小的文件。虽然您不必在两端使用相同大小的缓冲区，但在两端使用相同的代码。当您通过网络进行复制时，您可能会认为1k或1.5k是最佳大小，但忽略了内核中套接字发送和接收缓冲区的存在。当你考虑它们时，最好使用8k或更多。

Answer 2

我终于解决了这个问题。这是我修改的服务器和客户端源代码。希望这对其他人也有帮助！ :) 服务器端代码段（发件人）：

final File myFile= new File(filePath); //sdcard/DCIM.JPG
    byte[] mybytearray = new byte[8192];
    FileInputStream fis = new FileInputStream(myFile);  
    BufferedInputStream bis = new BufferedInputStream(fis);
    DataInputStream dis = new DataInputStream(bis);
    OutputStream os;
    try {
        os = socket.getOutputStream();
        DataOutputStream dos = new DataOutputStream(os);
        dos.writeUTF(myFile.getName());     
        dos.writeLong(mybytearray.length);
        int read;
        while((read = dis.read(mybytearray)) != -1){
            dos.write(mybytearray, 0, read);
        }

    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

客户端代码段（Receiver）：

int bytesRead;
    InputStream in;
    int bufferSize=0;

    try {
        bufferSize=socket.getReceiveBufferSize();
        in=socket.getInputStream();
        DataInputStream clientData = new DataInputStream(in);
        String fileName = clientData.readUTF();
        System.out.println(fileName);
        OutputStream output = new FileOutputStream("//home//evinish//Documents//Android//Received files//"+ fileName);
        byte[] buffer = new byte[bufferSize];
        int read;
        while((read = clientData.read(buffer)) != -1){
            output.write(buffer, 0, read);
        }

    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

写入输出流的速度有点快：

long acc=0;
long N=myFile.length();
 while(acc<N){
            noofbytes=dis.read(mybytearray, 0, 16384);
            dos.write(mybytearray, 0, noofbytes);
            acc=acc+noofbytes; } dos.flush();

我在传输72MB的视频文件时节省了大约7秒钟。

通过java套接字传输大文件

2 个答案: