java - 多个数据输入/输出流混淆

Question

我正在创建一个允许上传和下载到文件服务器的简单程序。我需要在服务器完全在线之前在上传和下载之间做出选择。问题是，我对数据输入/输出流等感到非常困惑，目前上传选项不起作用。它会自行运行，但不会按照我在此处编写的方式运行。在这个阶段它让我头疼!

服务器代码:

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

import javax.swing.JOptionPane;

 public class Server_Test {

public static void main(String a[]) throws Exception {

    int timeoutsecs = 600;
    int port = 4444;
    Socket sock;
    ServerSocket servsock = new ServerSocket(port, timeoutsecs);

    while (true) {

        // wait for the next client connection
        sock = servsock.accept();

        DataInputStream choice = new DataInputStream(sock.getInputStream());


        if (choice.read() == 1){

        // ****1*****
        // Download
        // Send I/O streams to the socket



        DataOutputStream out = new DataOutputStream(sock.getOutputStream());
        new Server_Test().sendFile(out);

        }else if (choice.read() == 2){

        // ****2****
        //Upload
        // Receive I/O streams from socket



        DataInputStream in = new DataInputStream(sock.getInputStream());
        new Server_Test().receiveFile(in);

        }

        // Close this connection, (not the overall // server socket)

        sock.close(); 

}
}

public void sendFile(DataOutputStream os) throws Exception{

     // String fileLoc = JOptionPane.showInputDialog(null, "What is the file location of the file you want to download?");
    File file = new File("C:\\TestFile.txt");
    FileInputStream fis = new FileInputStream(file);
    byte [] mybytearray  = new byte [(int)file.length()+1];

    BufferedInputStream bis = new BufferedInputStream(fis);

      bis.read(mybytearray,0,mybytearray.length);
      System.out.println("Sending...");
      os.write(mybytearray,0,mybytearray.length);
      os.flush();

    bis.close();


}

public void receiveFile(DataInputStream in) throws Exception{

    int filesize=6022386;
      int bytesRead;
      int current = 0;
      byte [] mybytearray  = new byte [filesize];

        FileOutputStream fos = new FileOutputStream("C:\\UploaTest.txt");
        BufferedOutputStream bos = new BufferedOutputStream(fos);
        bytesRead = in.read(mybytearray,0,mybytearray.length);
        current = bytesRead;


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

        bos.write(mybytearray, 0 , current);
        bos.flush();
        bos.close();

}

客户端代码:

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

import javax.swing.JOptionPane;

public class Client_Test {
public static void main(String a[]) throws Exception {

    Socket sock;


//  ServerSocket serverSocket = new ServerSocket(5556);

    sock = new Socket("127.0.0.1", 4444);
    System.out.println("Connecting...");

    Integer choice = Integer.parseInt(JOptionPane.showInputDialog(null, "Please type 1 for download and 2 for upload."));
    DataOutputStream outs = new DataOutputStream(sock.getOutputStream());



    outs.write(choice);
    //outs.flush();
    //outs.close();

    if(choice == 1){    

    // *****1*****
    //Download
    // Get I/O streams from the socket
    DataInputStream is = new DataInputStream(sock.getInputStream());
    // receive file
    new Client_Test().downloadFile(is);

    }else if(choice == 2){

    //*****2****
    //Upload
    //Send I/O streams to the socket.
    DataOutputStream out = new DataOutputStream(sock.getOutputStream());
    new Client_Test().uploadFile(out);

    }


    sock.close();
}

public void downloadFile(DataInputStream in) throws Exception{

     int filesize=6022386;
      int bytesRead;
      int current = 0;
      byte [] mybytearray  = new byte [filesize];

        FileOutputStream fos = new FileOutputStream("C:\\DowloadTest.txt");
        BufferedOutputStream bos = new BufferedOutputStream(fos);
        bytesRead = in.read(mybytearray,0,mybytearray.length);
        current = bytesRead;


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

        bos.write(mybytearray, 0 , current);
        bos.flush();
        bos.close();


}



public void uploadFile (DataOutputStream out)throws Exception{

    File file = new File("C:\\TestFile.txt");
    FileInputStream fis = new FileInputStream(file);
    byte [] mybytearray  = new byte [(int)file.length()+1];

    BufferedInputStream bis = new BufferedInputStream(fis);

      bis.read(mybytearray,0,mybytearray.length);
      System.out.println("Sending...");
      out.write(mybytearray,0,mybytearray.length);
      out.flush();


      bis.close();

}

}

Answer 1

您遇到的问题是由这些线路引起的:

if (choice.read() == 1){

和

  }else if (choice.read() == 2){

流阻塞直到数据可用，所以服务器在第一个 if 行等待。

当客户端随后发送 1 或 2 时，读取调用继续并将读取的值与 1 进行比较。如果您发送值 2，则比较为 false，服务器继续到第二行并阻塞等待更多输入。

您应该将两个读取调用替换为一个:

int choiceValue = choice.read();
if (choiceValue==1)
{
}
else if (choiceValue==2
{
}     

这应该可以解决您当前的问题。

我认为您的 Server_Test.receiveFile() 方法中可能存在另一个问题，因为看起来您正在尝试读取文件两次，一次是在这一行中

bytesRead = in.read(mybytearray,0,mybytearray.length);

然后再次循环:

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