java - 套接字文件传输 : Receiver stuck in reading from buffer/writing to storage

Question

static void sendFile(Socket socket, File file) throws IOException {

    File testFile = new File( Environment.getExternalStorageDirectory().toString()+"/DCIM/Camera/Test.jpg");
    byte [] buffer = new byte[(int)testFile.length()];
    FileInputStream fis = new FileInputStream(testFile);
    BufferedInputStream bis = new BufferedInputStream(fis);
    Log.d(DebugTag, "Trying to read testFile from storage into buffer");
    bis.read(buffer,0,buffer.length); 
    Log.d(DebugTag, "Read testFile into buffer");
    OutputStream os = socket.getOutputStream();
    Log.d(DebugTag, "Trying to write testFile from buffer into output stream");
    os.write(buffer, 0, buffer.length);
    Log.d(DebugTag, "Wrote testFile from buffer into output stream");
    os.flush();
    Log.d(DebugTag, "Outputstream flushed");
}

static void receiveFile(Socket socket) throws IOException {

    InputStream is = socket.getInputStream();
    String receivedFileDirectory = Environment.getExternalStorageDirectory().toString()+"/Pictures/receivedFile.jpg";
    File receivedFile = new File(receivedFileDirectory);
    //check if directory exists, otherwise create it
    if (receivedFile.exists()) {
        Log.d(DebugTag, "Filename at destination already exists");
    } else if (!receivedFile.exists()) {
        Log.d(DebugTag, "Filename at destination does not exist, trying to create it!");
        receivedFile.createNewFile();
        Log.d(DebugTag, "Created file!");
    }

    Log.d(DebugTag, "Preparing file reception. Destination:"+receivedFileDirectory);
    OutputStream os = new FileOutputStream(receivedFileDirectory);
    Log.d(DebugTag, "established outputstream to file directory");
    byte[] buffer = new byte[2048];
    int length;
    Log.d(DebugTag, "Trying to read inputstream into buffer and write file to destination");
    while ((length = is.read(buffer)) >0 ) {
        os.write(buffer,0,length);
    }
    Log.d(DebugTag, "File received.");
    os.flush();
    os.close();
    is.close();
    Log.d(DebugTag, "Closed in and out streams");

}

发件人文件似乎工作正常，我收到每条日志消息，直到“输出流刷新”。 在接收端，一切似乎都很顺利，直到代码到达 while 循环:我收到的最后一条日志消息始终是“尝试将输入流读入缓冲区并将文件写入目标”，但不是“已接收文件”和以下消息.奇怪的是:我收到测试文件并可以打开它(虽然需要几秒钟 - 不知道这是否是 android 的典型情况)。 有什么线索说明为什么代码会卡在 while 循环中吗？

第二个问题:这是我的第一个 Android/Java 应用程序。这段代码可以通过套接字发送和接收文件吗？即使文件变大(高达 >100MB)？

提前致谢!

Answer 1

is.read(buffer) 只有在正常关闭连接的另一端(或在错误时抛出异常)时才会返回零，所以你缺少的是 socket.close() 在发送端。

os.flush() 在这里是不够的，因为 TCP 不知道您何时完成发送数据。