Java套接字文件传输线程失败，但在调试时可以工作

Question

我不知道为什么我的程序在调试时可以工作，但在正常执行时却失败。

我已经设置了一个简单的服务器来通过套接字提供文件。当客户端连接时，启动一个线程来执行此任务，但它失败了。我收到“套接字已关闭”错误。

这是作业:在我弄清楚为什么会发生这种情况之前，我无法前进，并且只是想朝正确的方向插入。

为了让它在调试中工作，我在服务器类中设置了断点，它接受客户端连接。

提前致谢。

public class File_Server {

    private static ServerSocket servsock;

    public static void main(String[] args) throws IOException 
    {
        // create socket
    try {
        servsock = new ServerSocket(4444);
    } catch (Exception e) {
        System.out.println("Port already in use.");
        System.exit(1);
    }

    while (true) {
        System.out.println("Waiting...");
        try (Socket sock = servsock.accept()) {
            System.out.println("Accepted connection : " + sock);

            Thread t = new Thread(new CLIENTConnection(sock));

            t.start();

        } catch (Exception e) {
            System.out.println("Cannot accept connection.");
            }
        }
    }
}



public class CLIENTConnection implements Runnable {

    private Socket client;

    CLIENTConnection(Socket client) {
        this.client = client;
    }

    @Override
    public void run() 
    {
        try {
            FileInputStream fis = null;         
            // sendfile
            File myFile = new File("studentData.txt");
            byte[] mybytearray = new byte[(int) myFile.length()];
            fis = new FileInputStream(myFile);
            BufferedInputStream bis = new BufferedInputStream(fis);
            bis.read(mybytearray, 0, mybytearray.length);
            OutputStream os = client.getOutputStream();
            System.out.println("Sending...");
            os.write(mybytearray, 0, mybytearray.length);
            os.flush();
            fis.close();
        } catch (IOException ex) {
            Logger.getLogger(CLIENTConnection.class.getName()).log(Level.SEVERE, null, ex);
        } 
    }
}



public class File_Client {

    private static long start = System.currentTimeMillis();
    private static int bytesRead;
    private static int current = 0;

    public static void main(String[] args) throws IOException 
    {
        int filesize = 60223861; // filesize temporary hardcoded

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

            // receive file
            byte[] mybytearray = new byte[filesize];
            InputStream is = sock.getInputStream();
            FileOutputStream fos = new FileOutputStream("studentData-received.txt");
            try (BufferedOutputStream bos = new BufferedOutputStream(fos)) {
                bytesRead = is.read();//.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();
                long end = System.currentTimeMillis();
                System.out.println("Time taken " + (end - start) + " milliseconds");
            }
        } catch (Exception e) {
            System.out.println("Cannot connect to server.");
        }
    }
}

Answer 1

您犯了忽略 read() 结果的常见错误。它返回实际读取的字节数，或者在 EOS 处为 -1。 Java中复制流的方法如下:

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

其中“count”是一个整数。