Program architecture

Reads keystrokes from server. Creates screenshots, detects changes in them and sends changed tiles (128x128px by default) to the server.

Two threads: GUI thread and ClientWorker, communicating with queues.

• Queue<byte[]> received
  • filled by ClientWorker with messages from the server
  • read by GUI thread
  • contains keystrokes and mouse instructions, they are to be performed
• Queue<byte[]> tosend
  • filled by GUI thread
  • read by ClientWorker, the messages are sent to server
  • contains bitmap tiles to be sent to the server

ClientWorker thread:

• perform SSL handshake
• enter an infinite loop:
  • send data from “tosend” queue
  • if some data in socket are available, put them to “received” queue

GUI thread:

• on timer1.tick():
  • if some data (keystrokes or mouse instructions) are available in the “received” queue, process them
  • if “tosend” queue is empty (this is to prevent network congestion)
    • create screenshot
    • break it to 128x128px tiles
    • compare with previous screenshot
    • add changed tiles to “tosend” queue

Displays tiles received from client. Forwards KeyPress and MouseClick events to the client.

Two threads: GUI thread and ServerWorker, communicating with queues.

• Queue<byte[]> received
  • filled by ServerWorker with messages from the client
  • read by GUI thread
  • contains bitmap tiles to be displayed
• Queue<byte[]> tosend
  • filled by GUI thread
  • read by ServerWorker, the messages are sent to client
  • contains keystrokes and mouse instructions

ServerWorker thread:

• listen on socket, perform SSL handshake
• read data from socket asynchronously, put them to “readData” queue
• enter infinite loop:
  • read “readData” queue, put messages to “received” queue
  • if “tosend” queue is not empty, send data from it to client

GUI thread:

• on timer1.tick():
  • get tiles from “received” queue, display them in picturebox
• on MouseUp, MouseDown or KeyPress:
  • add the event to “tosend” queue

Datagram format: 4B magic value “0x95400954”, 4B length, 4B type, lengthB-4 payload

payload: 2B format, 2B xstart, 2B ystart, 2B width, 2B height, data

format: 0x1 = JPEG

Contains image data to be displayed.

payload: nothing

payload: 2B X, 2B Y, 4B flags

payload: text to be typed on the keyboard

payload: nothing

Forces client to resend all tiles again.

• https://msdn.microsoft.com/en-us/library/bew39x2a%28v=vs.110%29.aspx
• https://msdn.microsoft.com/en-us/library/fx6588te%28v=vs.110%29.aspx
• https://stackoverflow.com/questions/2416748/how-to-simulate-mouse-click-in-c
• https://msdn.microsoft.com/en-us/library/ms171548%28v=vs.110%29.aspx
• http://ksvi.mff.cuni.cz/~holan/ (Czech)
• https://stackoverflow.com/questions/5461338/how-to-create-a-jpg-image-dynamically-in-memory-with-net
• https://stackoverflow.com/questions/362986/capture-the-screen-into-a-bitmap
• https://msdn.microsoft.com/en-us/library/kb5kfec7%28v=vs.110%29.aspx
• https://msdn.microsoft.com/en-us/library/5ey6h79d%28v=vs.110%29.aspx
• https://stackoverflow.com/questions/695802/using-ssl-and-sslstream-for-peer-to-peer-authentication
• http://blogs.msdn.com/b/joncole/archive/2007/06/13/sample-asynchronous-sslstream-client-server-implementation.aspx
• https://msdn.microsoft.com/en-us/library/system.net.security.sslstream.aspx
• https://www.sslshopper.com/article-most-common-openssl-commands.html
• https://stackoverflow.com/questions/6686356/sslstream-equivelent-of-tcpclient-available