Detailed explanation of the C# implementation of packet encryption and decryption examples

using System;
using ;
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namespace EncryptDataReport
{
  public partial class Form1 : Form
  {
    public Form1()
    {
      InitializeComponent();
    }
    #region Define global objects and variables    private IPEndPoint Server;// Server side    private IPEndPoint Client;//Client    private Socket mySocket;//Socket    private EndPoint ClientIP;//IP address    byte[] buffer, data;//Receive cache    bool blFlag = true;//Identify whether the message is sent for the first time    bool ISPort = false;//Judge the port is open    int SendNum1, ReceiveNum1, DisNum1; //Record the sent\received\lost datagrams when the form is loaded    int SendNum2, ReceiveNum2, DisNum2; //Record the currently sent\received\lost datagram    int SendNum3, ReceiveNum3, DisNum3; //Cached sent\received\lost datagram    int port;//Port number    #endregion
    //Asynchronously receive information    private void StartLister(IAsyncResult IAResult)
    {
      int Num = (IAResult, ref ClientIP);
      string strInfo = (buffer, 0, Num);
      ("user" + ());
      ("：");
      ("\r\n");
      (DecryptDES(strInfo, "mrsoftxk"));//Decrypt the received information      ("\r\n");
      (buffer, 0, , , ref ClientIP, new AsyncCallback(StartLister), null);
    }
    //Initialize sent, received and lost datagrams    private void Form1_Load(object sender, EventArgs e)
    {
      if (blFlag == true)
      {
        IPGlobalProperties NetInfo = ();
        UdpStatistics myUdpStat = null;
        myUdpStat = NetInfo.GetUdpIPv4Statistics();
        SendNum1 = (());
        ReceiveNum1 = (());
        DisNum1 = (());
      }
    }
    //Set the port number    private void button4_Click(object sender, EventArgs e)
    {
      try
      {
        port = Convert.ToInt32();
        CheckForIllegalCrossThreadCalls = false;
        buffer = new byte[1024];
        data = new byte[1024];
        Server = new IPEndPoint(, port);
        Client = new IPEndPoint(, port);
        ClientIP = (EndPoint)Server;
        mySocket = new Socket(, , );
        (, , 1);
        (Server);
        (buffer, 0, , , ref ClientIP, new AsyncCallback(StartLister), null);
        ISPort = true;//Open the specified port number      }
      catch { }
    }
    //Send information    private void button2_Click(object sender, EventArgs e)
    {
      if (ISPort == true)//Judge whether there is an open port number      {
        IPGlobalProperties NetInfo = ();
        UdpStatistics myUdpStat = null;
        myUdpStat = NetInfo.GetUdpIPv4Statistics();
        try
        {
          if (blFlag == false)//Not first time send          {
            SendNum2 = (());
            ReceiveNum2 = (());
            DisNum2 = (());
             = (SendNum2 - SendNum3);
             = (ReceiveNum2 - ReceiveNum3);
             = (DisNum2 - DisNum3);
          }
          SendNum2 = (());
          ReceiveNum2 = (());
          DisNum2 = (());
          SendNum3 = SendNum2; //Record this sending datagram          ReceiveNum3 = ReceiveNum2;//Record this received datagram          DisNum3 = DisNum2; //Record this lost datagram          if (blFlag == true)//First send          {
             = (SendNum2 - SendNum1);
             = (ReceiveNum2 - ReceiveNum1);
             = (DisNum2 - DisNum1);
            blFlag = false;
          }
        }
        catch (Exception ex)
        {
          (, "Prompt message", , );
        }
        string str = EncryptDES(, "mrsoftxk");//Encrypt the information to be sent        data = (str);
        (data, , , Client);
         = "";
      }
      else
      {
        ("Please open the port first!", "hint", , );
        ();
      }
    }
    //Clear the screen    private void button1_Click(object sender, EventArgs e)
    {
      ();
    }
    //quit    private void button3_Click(object sender, EventArgs e)
    {
      ();
    }
    //Press the <Ctrl+Enter> key combination to send information    private void rtbSend_KeyDown(object sender, KeyEventArgs e)
    {
      //Send a message when Ctrl and Enter are pressed at the same time      if ( &amp;&amp;  == 13)
      {
         = true;
        button2_Click(this, null);
      }
    }
    //Cha record scrolls at any time    private void rtbContent_TextChanged(object sender, EventArgs e)
    {
      ();
    }
    private static byte[] Keys = { 0x12, 0x34, 0x56, 0x78, 0x90, 0xAB, 0xCD, 0xEF };//Key    #region DES encryption string    ///&lt;summary&gt;  
    ///DES encryption string    ///&lt;/summary&gt;  
    ///<param name="str">String to be encrypted</param>    ///<param name="key">Encryption key, required to be 8 bits</param>    ///<returns> Encryption successfully returns the encrypted string, and fails to return the source string</returns>    public string EncryptDES(string str, string key)
    {
      try
      {
        byte[] rgbKey = Encoding.((0, 8));
        byte[] rgbIV = Keys;
        byte[] inputByteArray = Encoding.(str);
        DESCryptoServiceProvider myDES = new DESCryptoServiceProvider();
        MemoryStream MStream = new MemoryStream();
        CryptoStream CStream = new CryptoStream(MStream, (rgbKey, rgbIV), );
        (inputByteArray, 0, );
        ();
        return Convert.ToBase64String(());
      }
      catch
      {
        return str;
      }
    }
    #endregion
    #region DES decryption string    ///&lt;summary&gt;  
    ///DES decryption string    ///&lt;/summary&gt;  
    ///<param name="str">String to be decrypted</param>    ///<param name="key">Decryption key, required to be 8 bits, the same as the encryption key</param>    ///<returns>The decryption successfully returns the decrypted string, and the source string is returned to the failed</returns>    public string DecryptDES(string str, string key)
    {
      try
      {
        byte[] rgbKey = Encoding.(key);
        byte[] rgbIV = Keys;
        byte[] inputByteArray = Convert.FromBase64String(str);
        DESCryptoServiceProvider myDES = new DESCryptoServiceProvider();
        MemoryStream MStream = new MemoryStream();
        CryptoStream CStream = new CryptoStream(MStream, (rgbKey, rgbIV), );
        (inputByteArray, 0, );
        ();
        return Encoding.(());
      }
      catch
      {
        return str;
      }
    }
    #endregion
  }
}