将一堆图像从Android手机发送到PC

Question

I'm working on an app that suppose to transfer images from an android phone to a PC in a server - client architecture (the java (android) code is added below).The photos suppose to pass through a bytearray. I'm having a hard time to figure out how to create a protocol over TCP that will be able to pass my images without loss of information and also be able to pass the META-DATA of the images such as the image name, extension, size, maybe META-DATA size (if needed?). I would really appreciate your help becuase I'm kind of new to C# and writing a client-server, especially one that suppose to transfer images of some sorts of extensions.

private void makeTCPConnection() {
        try {
            InetAddress serverAddr = InetAddress.getByName("10.0.2.2");
            //create a socket to make the connection with the server
            Socket socket = new Socket(serverAddr, 8000);

            try {
                //Sends the message to the server
                OutputStream output = socket.getOutputStream();
                File dcim = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DCIM);
                if(dcim == null)
                    return;
                File[] pics=dcim.listFiles();
                int count=0;
                if(pics != null){
                    for(File pic:pics){

                    FileInputStream fis = new FileInputStream(pic);
                    Bitmap bm = BitmapFactory.decodeStream(fis);
                    byte[] imgbyte = getBytesFromBitmap(bm);
                    output.write(imgbyte);
                    output.flush();
                    }
                }
            }catch (Exception e){
             Log.e("TCP","S:Error",e);
            }finally {
                socket.close();
            }
        }catch (Exception e){
            Log.e("TCP","C:Error",e);
        }
    }

    public byte[] getBytesFromBitmap(Bitmap bitmap){
        ByteArrayOutputStream stream = new ByteArrayOutputStream();
        bitmap.compress(Bitmap.CompressFormat.PNG,70,stream);
        return stream.toByteArray();
    }

Answer 1

Have you considered to write a small REST web service ?

This approach would have some advantages:

• HTTP (human-readable) is used as a protocol, so you don't have to come up with an own protocol.
• JSON (human-readable) can be used transmit data. (Maybe not for photos, but for metadata.)
• There are plenty libraries for the client and server side.
• Client and server can be written in different languages.
• In some languages a REST web service can be created with just a few lines of code.
• The REST web service can be written first and can be tested (with a REST client), before writing the client application.
• More REST endpoints can be added easily. (Maybe you build a simple upload first and later add more endpoints to upload metadata.)

For Android I can recommend Retrofit as a REST client. And if you want to use Java on the server side, I would recommend Spring/Spring Boot . (How-to guide for a REST web service in Spring Boot: https://spring.io/guides/gs/rest-service/ )