C#

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Runtime.Remoting;
using System.Linq;
using System.Text;
using System.Net .Sockets ;
using System.Windows.Forms;
using System.Threading ;
using System.Runtime.Serialization.Formatters.Binary;
using System.Net;


namespace simpleserver
{
    public partial class Form2 : Form
    {
        private readonly    int port;
        private TcpClient client;
        private TcpListener server;
        //static public int MAX_CONN = 5;
        private NetworkStream mainstream;
        //private string ipList;
        //TcpListener myList = null;


//static int thrd = -1;

        private readonly Thread Listening;
        private readonly Thread Getimg;
        public Form2(int Port)
        {
            port = Port;
            client = new TcpClient();
            Listening = new Thread(StartListening);
            Getimg = new Thread(ReceiveImage);
            InitializeComponent();
        }


        private void StartListening()
        {
            while (!client.Connected)
            {
                //ipList = new string[MAX_CONN];
                //myList = new TcpListener(hostIP, hostPort);
                //myList.Start();

               server.Start();
               client = server.AcceptTcpClient();

               
            }
            Getimg.Start();
            
        }
        private void stop()
        {
            server.Stop();
            client = null;
            if (Listening .IsAlive )Listening .Abort ();
            if ( Getimg .IsAlive )Getimg .Abort ();
        }
        private void ReceiveImage()
        {
            BinaryFormatter binformatter = new BinaryFormatter();
            while (client.Connected)
            {
                mainstream = client.GetStream();
                pictureBox1.Image =(Image ) binformatter.Deserialize(mainstream);
              //  pictureBox2 .Image =(Image )binformatter .Deserialize (mainstream );

            }
 
        }
        protected override void OnLoad(EventArgs e)
        {
            base.OnLoad(e);
            server = new TcpListener(IPAddress .Any ,port  );
            Listening .Start ();
        }

      
    }
}

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Drawing.Imaging;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Net.Sockets;
using System.Runtime.Serialization.Formatters.Binary;

namespace sampleclient
{
    public partial class Form1 : Form
    {
        private readonly TcpClient client = new TcpClient();
        private NetworkStream mainStream;
        private int portNumber;

        private static Image GetDesktop()
        {
            Rectangle bounds = Screen.PrimaryScreen.Bounds;
            Bitmap screenshot = new Bitmap(bounds .Width ,bounds .Height,PixelFormat .Format32bppArgb );
            Graphics g = Graphics.FromImage(screenshot);
            g.CopyFromScreen(bounds.X, bounds.Y, 0, 0, bounds.Size, CopyPixelOperation.SourceCopy);
            return screenshot;
        }
        private void SendDesktop()
        {
            
            BinaryFormatter  binformatter = new BinaryFormatter ();
            mainStream = client.GetStream();
            binformatter.Serialize (mainStream, GetDesktop());

 
        }

        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            portNumber = int.Parse(textBox2.Text);
            try
            {
                client.Connect(textBox1.Text, portNumber);
                MessageBox.Show("connected success");
                timer1.Start();
            }
            catch (Exception)
            {
                MessageBox.Show("fail");
            }
        }

        //private void button2_Click(object sender, EventArgs e)
        //{
        //    if (button2.Text.StartsWith("share")) 
        //    {
        //        timer1.Start();
        //        button2.Text = ("stop sha");
        //    }
        //    else 
        //    {
        //        timer1 .Stop ();
        //        button2 .Text ="share sceen";
        //    }
        //}

        private void timer1_Tick(object sender, EventArgs e)
        {
            SendDesktop ();
        }
    }

}

[DllImport("Crypt32.dll", SetLastError = true)]
private static extern bool CryptProtectData([MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef=typeof(ByteArrayToDataBlobMarshaler))] byte[] pDataIn, [Optional] string szDataDescr, [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef=typeof(ByteArrayToDataBlobMarshaler)), Optional] byte[] pOptionalEntropy, IntPtr pvReserved, [Optional] IntPtr pPromptStruct, int dwFlags, [In, MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef=typeof(ByteArrayToDataBlobMarshaler)), Out] byte[] pDataOut);

[DllImport("Crypt32.dll", SetLastError = true)]
private static extern bool CryptUnprotectData([MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef=typeof(ByteArrayToDataBlobMarshaler))] byte[] pDataIn, [Optional] string ppszDataDescr, [MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef=typeof(ByteArrayToDataBlobMarshaler)), Optional] byte[] pOptionalEntropy, IntPtr pvReserved, [Optional] IntPtr pPromptStruct, int dwFlags, [In, MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef=typeof(ByteArrayToDataBlobMarshaler)), Out] byte[] pDataOut);

public object MarshalNativeToManaged(IntPtr pNativeData)
{
    if (pNativeData == IntPtr.Zero) { return null; }
    int length = Marshal.ReadInt32(pNativeData);
    byte[] data = new byte[length];
    IntPtr dataPtr = Marshal.ReadIntPtr(pNativeData, IntPtr.Size);
    Marshal.Copy(dataPtr, data, 0, length);
    return data;
}

byte[] clearBytes = Encoding.Unicode.GetBytes(clearText);
byte[] cipherBytes = new byte[0];
if (CryptProtectData(clearBytes, null, null, IntPtr.Zero, IntPtr.Zero, 0, cipherBytes))

[DllImport("Crypt32.dll", SetLastError = true, EntryPoint = "CryptProtectData")]
private static extern bool CryptProtectData4([MarshalAs(UnmanagedType.LPStruct), Out] DataBlob pDataIn, [Optional] string szDataDescr, [MarshalAs(UnmanagedType.LPStruct), Optional] DataBlob pOptionalEntropy, IntPtr pvReserved, [Optional] IntPtr pPromptStruct, int dwFlags, [MarshalAs(UnmanagedType.LPStruct), Out] DataBlob pDataOut);
[DllImport("Crypt32.dll", SetLastError = true, EntryPoint = "CryptUnprotectData")]
private static extern bool CryptUnprotectData4([MarshalAs(UnmanagedType.LPStruct), Out] DataBlob pDataIn, [Optional] string ppszDataDescr, [MarshalAs(UnmanagedType.LPStruct), Optional] DataBlob pOptionalEntropy, IntPtr pvReserved, [Optional] IntPtr pPromptStruct, int dwFlags, [MarshalAs(UnmanagedType.LPStruct), Out] DataBlob pDataOut);

[StructLayout(LayoutKind.Sequential)]
internal class DataBlob
{
    [MarshalAs(UnmanagedType.U4)]
    private int Length;
    private IntPtr Data;
}

string clearText = "TestString";
byte[] clearBytes = Encoding.Unicode.GetBytes(clearText);
DataBlob clearBlob = new DataBlob(clearBytes);
DataBlob cipherBlob = new DataBlob();
CryptProtectData4(clearBlob, null, null, IntPtr.Zero, IntPtr.Zero, 0, cipherBlob);
byte[] cipherBytes = cipherBlob.GetData();