title: Asynchronous Socket With TLS/SSL
body: <p>I saw examples programs on MSDN: Asynchronous Socket as below. I've tried the program and run normally. Is it possible Asynchronous Socket to be modified in order to support TLS/SSL? How to do it?</p>
  
  <pre><code>using System;
  using System.Net;
  using System.Net.Sockets;
  using System.Text;
  using System.Threading;
  
  // State object for reading client data asynchronously
  public class StateObject {
      // Client  socket.
      public Socket workSocket = null;
  
      // Size of receive buffer.
      public const int BufferSize = 1024;
  
      // Receive buffer.
      public byte[] buffer = new byte[BufferSize];
  
      // Received data string.
      public StringBuilder sb = new StringBuilder();  
  }
  
  public class AsynchronousSocketListener {
      // Thread signal.
      public static ManualResetEvent allDone = new ManualResetEvent(false);
  
      public static void StartListening() {
          // Data buffer for incoming data.
          byte[] bytes = new Byte[1024];
  
          // Establish the local endpoint for the socket.
          // The DNS name of the computer
          // running the listener is "host.contoso.com".
          IPHostEntry ipHostInfo = Dns.Resolve(Dns.GetHostName());
          IPAddress ipAddress = ipHostInfo.AddressList[0];
          IPEndPoint localEndPoint = new IPEndPoint(ipAddress, 11000);
  
          // Create a TCP/IP socket.
          Socket listener = new Socket(AddressFamily.InterNetwork,
          SocketType.Stream, ProtocolType.Tcp );
  
          // Bind the socket to the local endpoint and listen for incoming connections.
          try {
              listener.Bind(localEndPoint);
              listener.Listen(100);
  
              while (true) {
                  // Set the event to nonsignaled state.
                  allDone.Reset();
  
                  // Start an asynchronous socket to listen for connections.
                  Console.WriteLine("Waiting for a connection...");
  
                  listener.BeginAccept(new AsyncCallback(AcceptCallback), listener );
  
                  // Wait until a connection is made before continuing.
                  allDone.WaitOne();
              }
          } 
          catch (Exception e) {
              Console.WriteLine(e.ToString());
          }
  
          Console.WriteLine("\nPress ENTER to continue...");
          Console.Read();    
      }
  
      public static void AcceptCallback(IAsyncResult ar) {
          // Signal the main thread to continue.
          allDone.Set();
  
          // Get the socket that handles the client request.
          Socket listener = (Socket) ar.AsyncState;
          Socket handler = listener.EndAccept(ar);
  
          // Create the state object.
          StateObject state = new StateObject();
          state.workSocket = handler;
          handler.BeginReceive( state.buffer, 0, StateObject.BufferSize, 0,
          new AsyncCallback(ReadCallback), state);
      }
  
      public static void ReadCallback(IAsyncResult ar) {
          String content = String.Empty;
  
          // Retrieve the state object and the handler socket
          // from the asynchronous state object.
          StateObject state = (StateObject) ar.AsyncState;
          Socket handler = state.workSocket;
  
          // Read data from the client socket. 
          int bytesRead = handler.EndReceive(ar);
  
          if (bytesRead &gt; 0) {
              // There  might be more data, so store the data received so far.
              state.sb.Append(Encoding.ASCII.GetString(
              state.buffer,0,bytesRead));
  
              // Check for end-of-file tag. If it is not there, read 
              // more data.
              content = state.sb.ToString();
              if (content.IndexOf("&lt;EOF&gt;") &gt; -1) {
                  // All the data has been read from the 
                  // client. Display it on the console.
                  Console.WriteLine("Read {0} bytes from socket. \n Data : {1}",
                  content.Length, content );
                  // Echo the data back to the client.
                  Send(handler, content);
              } 
              else {
                  // Not all data received. Get more.
                  handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,
                  new AsyncCallback(ReadCallback), state);
              }
          }
      }
  
      private static void Send(Socket handler, String data) {
          // Convert the string data to byte data using ASCII encoding.
          byte[] byteData = Encoding.ASCII.GetBytes(data);
  
          // Begin sending the data to the remote device.
          handler.BeginSend(byteData, 0, byteData.Length, 0,
          new AsyncCallback(SendCallback), handler);
      }
  
      private static void SendCallback(IAsyncResult ar) {
          try {
              // Retrieve the socket from the state object.
              Socket handler = (Socket) ar.AsyncState;
  
              // Complete sending the data to the remote device.
              int bytesSent = handler.EndSend(ar);
              Console.WriteLine("Sent {0} bytes to client.", bytesSent);
  
              handler.Shutdown(SocketShutdown.Both);
              handler.Close();
  
          } 
          catch (Exception e) {
              Console.WriteLine(e.ToString());
          }
      }
  
  
      public static int Main(String[] args) {
          StartListening();
          return 0;
      }
  }
  </code></pre>