Writing my own Screen Sharing Server and Protocol

Question

I'm building a client/server solution which needs to have screen sharing functionality. I have something already "working" but the problem is that it only works over internal network, because my methodology is not fast enough.

What I am basically doing is that the client makes a request for the server asking for a screen image each 5 seconds (for example). And this is the code which is processed once this requests are received:

private void GetImage(object networkstream)
{
    NetworkStream network = (NetworkStream)networkstream;

    Bitmap bitmap = new Bitmap(
        SystemInformation.PrimaryMonitorSize.Width,
        SystemInformation.PrimaryMonitorSize.Height);
    Graphics g = Graphics.FromImage(bitmap);
    g.CopyFromScreen(new Point(0, 0), new Point(0, 0), bitmap.Size);
    g.Flush();
    g.Dispose();

    MemoryStream ms = new MemoryStream();
    bitmap.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
    bitmap.Dispose();

    byte[] array = ms.ToArray();

    network.Write(array, 0, array.Length);
    network.Flush();

    ms.Dispose();
}

What are best methods to do what I'm trying to? I need to get at least 0.2 FPS (refresh each 5 seconds) Obs.: I'm using Windows Forms and it is being done over sockets.
How do TeamViwer and .rdp files work?

@PinnyM Yes, but he wants to do it really slowly. Presumably he's only sharing PowerPoint presentations ;) — RB., Feb 12 '13 at 15:33
This looks interesting, from Vista there is an API: http://www.teknoportal.gen.tr/english/technology_news.asp?haber=385 — George Duckett, Feb 12 '13 at 15:36

score 2 · Accepted Answer · edited May 23 '17 at 12:14

2

You can send only difference betwen present and last image. Look here: Calculate image differences in C#

If it wont be fast enough, you can divide your screen into smallers, like 100x100 or 50x50 bitmaps, check if this area had changed and if yes just send it to client.

edited May 23 '17 at 12:14

Community

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answered Feb 12 '13 at 15:36

Mateusz Krzaczek

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score 2 · Answer 2 · answered Feb 12 '13 at 15:37

You need to optimize your protocol, here are some suggestions:

break the input image in segments, send segments instead of full screen
only send a segment if it's different from the previously sent version
use http notification type of communication where your viewer sends a request but only gets a response if the server received new segments from the presenter, possibly several grouped together.
compress the image data, don't transmit raw
give users the option to choose the level of compression to speed things up or to get a better image
I doubt this would be in your budget but you can also encode the stream as streaming video

score 2 · Answer 3 · answered Feb 12 '13 at 18:35

2

What about using an existing implementation? Or learning from it? http://cdot.senecac.on.ca/projects/vncsharp/

answered Feb 12 '13 at 18:35

delixfe

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Writing my own Screen Sharing Server and Protocol

3 Answers3