如何进行循环以从服务器（在客户端-服务器应用程序中）读取/下载文件？

Question

In my client-server application, the client sends GET filename command to the server in order to download the file. Now the client must be able to read the buffer size (of file residing in server) and download it into the client. That's I have done inside a while loop. My concern is about that loop in client class: Is the looping correct? The way I am reading the file ...?

I think I should specify the filesize inside the loop. Then how it could be done or improved?

This is the portion of code I am working on.

ClientSide:

 if (request.startsWith("GET")) {
                    File file = new File(request.substring(4));
                        is = socket.getInputStream();
                        fos = new FileOutputStream(file);

                        byte[] buffer = new byte[socket.getReceiveBufferSize()];
                        int bytesReceived = 0;
                        while ((bytesReceived = is.read(buffer)) >=0) {
                            //while ((bytesReceived = is.read(buffer))>=buffer) {
                            fos.write(buffer, 0, bytesReceived);
                        }
                        request = "";
                        fos.close();
                        is.close();


     }

ServerSide:

  try (FileInputStream fis = new FileInputStream(file)) {
                            os = socket.getOutputStream();
                            byte[] buffer = new byte[(1 << 7) - 1];
                            int bytesRead = 0;

                            while ((bytesRead = fis.read(buffer)) != -1) {
                                os.write(buffer, 0, bytesRead);
                            }

                        }

Answer 1

If this is an implementation of HTTP protocol, the client might not not the size of the file, which is being send by the server. One approach is the server always sends "Content-Length" header and client reads up to this length.More info HTTP specification: http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html The other approach is client reads until the connection is closed by the server. When server sends the whole file, it closes the connection. This is not very reliable, as connection might be dropped due to network problem.