using System;

 using System.Collections.Generic;

 using System.ComponentModel;

 using System.Data;

 using System.Drawing;

 using System.Linq;

 using System.Text;

 using System.Threading.Tasks;

 using System.Windows.Forms;

 using System.Runtime.InteropServices;

 using System.IO;  //The following four usings are important.So are they in Reciever and dll.

 using System.Runtime.Serialization.Formatters.Binary;

 using System.Runtime.Serialization;

 using ClassLibrary1;

 namespace cdn_send

 {

     public partial class Form1 : Form

     {

         public Form1()

         {

             InitializeComponent();

         }        

         private void Form1_Load(object sender, EventArgs e)

         {

         }

         private const int WM_COPYDATA = 0x004A;

         private const uint flag = 0x8000; //I can't understand it.Please tell me(if you got it).

         [DllImport("User32.dll", EntryPoint = "SendMessage")]

         private static extern int SendMessage(int hWnd, int Msg, int wParam, ref COPYDATASTRUCT lParam);

         [DllImport("User32.dll", EntryPoint = "FindWindow")]

         private static extern int FindWindow(string lpClassName, string lpWindowName);

         [DllImport("kernel32.dll")]

         static extern uint GetTickCount();

         private void button1_Click(object sender, EventArgs e)

         {

             int WINDOW_HANDLER = FindWindow(null, @"xxx");  //Find target window.Well,by the way,it's called 'xxx'.

             if (WINDOW_HANDLER == )

             {

                 MessageBox.Show("xxx");

             }

             else

             {

                 data dd=new data();  //Process data.

                 dd.x = (int)this.Handle;

                 dd.y = DateTime.Now;

                 dd.tx = textBox1.Text;

                 dd.tk = GetTickCount();

                 byte[] bt=(new switcher()).Object2Bytes((object)dd);  //Type switch.

                 COPYDATASTRUCT cds;

                 cds.dwData = (IntPtr)flag;

                 cds.cbData = bt.Length;

                 cds.lpData = Marshal.AllocHGlobal(bt.Length);  //Allocate space.

                 Marshal.Copy(bt, , cds.lpData, bt.Length);  //Memory copy.

                 SendMessage(WINDOW_HANDLER, WM_COPYDATA, , ref cds);  //Send message out.

             }

         }

     }

 }

 using System;

 using System.Collections.Generic;

 using System.ComponentModel;

 using System.Data;

 using System.Drawing;

 using System.Linq;

 using System.Text;

 using System.Threading.Tasks;

 using System.Windows.Forms;

 using System.Runtime.InteropServices;

 using System.IO;  //Important.

 using System.Runtime.Serialization.Formatters.Binary;

 using System.Runtime.Serialization;

 using ClassLibrary1;

 namespace cdn_receiver

 {

     public partial class Form1 : Form

     {

         public Form1()

         {

             InitializeComponent();

         }

         private void Form1_Load(object sender, EventArgs e)

         {

         }

         const int WM_COPYDATA = 0x004A;

         private const uint flag = 0x8000;

         [DllImport("kernel32.dll")]

         public static extern uint GetTickCount();

         protected override void DefWndProc(ref System.Windows.Forms.Message m)

         {

             switch (m.Msg)

             {

                 case WM_COPYDATA:

                     COPYDATASTRUCT cds = new COPYDATASTRUCT();

                     cds = (COPYDATASTRUCT)m.GetLParam(cds.GetType()); //Receive information.

                     byte[] bt = new byte[cds.cbData];

                     Marshal.Copy(cds.lpData,bt,,bt.Length);  //Get data array.

                     data dd = (data)((new switcher()).Bytes2Object(bt));  //Transform back.

                     long xx = GetTickCount() - dd.tk;  //This line is used to calculate its delay,although mostly it is 0ms.

                     textBox1.Text = (dd.x.ToString() + " " + dd.y.ToString() + " " + dd.tx);

                     textBox1.Text += "\r\n" + xx.ToString() + "ms";

                     break;

                 default:

                     base.DefWndProc(ref m);  //Don't forget this line,or it cannot run properly.

                     break;

             }

         }

     }

 }

 using System;

 using System.Collections.Generic;

 using System.Linq;

 using System.Text;

 using System.Threading.Tasks;

 using System.Runtime.InteropServices;

 using System.Runtime;

 using System.IO; //Important

 using System.Runtime.Serialization;

 using System.Runtime.Serialization.Formatters.Binary;

 namespace ClassLibrary1

 {

     [Serializable]  //My datastructure which contains different types.Don't forget this line.

     public struct data

     {

         public int x;

         public DateTime y;

         public string tx;

         public long tk;

     }

     [StructLayout(LayoutKind.Sequential)]  //The datastructure which used as a media to transport.

     public struct COPYDATASTRUCT

     {

         public IntPtr dwData;

         public int cbData;

         public IntPtr lpData;

     }

     public class switcher  //The switcher object which contains two main switcher function.

     {

         public byte[] Object2Bytes(object obj)

         {

             IFormatter fmt = new BinaryFormatter();

             MemoryStream ms = new MemoryStream();

             fmt.Serialize(ms, obj);

             return ms.GetBuffer();

         }

         public object Bytes2Object(byte[] bt)

         {

             IFormatter fmt = new BinaryFormatter();

             MemoryStream ms = new MemoryStream(bt);

             return (object)fmt.Deserialize(ms);

         }

         public switcher(){

         }

     }

 }