static void Main(string[] args)
{
    // Start TCP server
    TcpListener listener = new TcpListener(IPAddress.Any, 1300);
    listener.Start();
    Console.WriteLine("Server started listening on port 1300.");
    // Wait for a client to connect on TCP port 1300
    TcpClient clientSocket = listener.AcceptTcpClient();
    if (clientSocket != null)
    {
        // We have a client application
        // Let's read some data. Note: since we don't start a new
        // thread to do this and call listener.AcceptTcpClient() again
        // no other client is able to connect. To do this, we have to create
        // multiple threads and call AcceptTcpClient over and over again for every
        // client.
        HandleClient(clientSocket);
    }
    // Stop listening
    listener.Stop();
    Console.WriteLine("\nServer stopped.");
}
static void HandleClient(TcpClient client)
{
    // Create an object from the (server) certificate file
    // To create this, you will need the appropriate password
    // Note: To make this demo work, you'll need to import this certificate
    // by right clicking the file and choose 'Install PFX', use the password as shown
    // below.
    X509Certificate certificate = new X509Certificate("..\\path\\tp\\Certificate.pfx", "ThisPasswordIsTheSameForInstallingTheCertificate");
    // Create a stream to decrypt the data
    using (SslStream sslStream = new SslStream(client.GetStream(), false,
        new RemoteCertificateValidationCallback(ValidateClientCertificate), null))
    {
        // Set a client certificate as mandatory
        sslStream.AuthenticateAsServer(certificate, true, System.Security.Authentication.SslProtocols.Ssl3, true);
        // Somehow the client.Connected is always true, therefore we
        // check for the '#' character, that will disconnect the client
        int b = 0;
        while ((char) b != '#')
        {
            b = sslStream.ReadByte();
            if (b > -1)
                Console.Write((char)b);
        }
    }
}
// The following method is invoked by the RemoteCertificateValidationDelegate.
// This allows you to check the certificate and accept or reject it
// return true will accept the certificate
public static bool ValidateClientCertificate(object sender, X509Certificate certificate,
    X509Chain chain, SslPolicyErrors sslPolicyErrors)
{
    // Accept all certificates
    return true;
}

static void Main(string[] args)
{
    // Connect as client to port 1300
    string server = "127.0.0.1";
    TcpClient client = new TcpClient(server, 1300);
   
    // Create a secure stream
    X509CertificateCollection cCollection = new X509CertificateCollection();
    cCollection.Add(new X509Certificate("..\\path\\tp\\Certificate.pfx", "ThisPasswordIsTheSameForInstallingTheCertificate"));
    using (SslStream sslStream = new SslStream(client.GetStream(), false,
        new RemoteCertificateValidationCallback(ValidateServerCertificate), null))
    {
        // Add a client certificate to the ssl connection
        sslStream.AuthenticateAsClient(server, cCollection, System.Security.Authentication.SslProtocols.Default, true);
        Console.WriteLine("Begin to type. All data will be send to the server. Type a '#' to stop.");
        char character = ' ';
        while (character != '#')
        {
            ConsoleKeyInfo info = Console.ReadKey();
            character = info.KeyChar;
            // Send the character over the encrypted stream
            sslStream.WriteByte((byte) character);
        }
    }
    // Disconnect and close the client
    client.Close();
}
// The following method is invoked by the RemoteCertificateValidationDelegate.
// This allows you to check the certificate and accept or reject it
// return true will accept the certificate
public static bool ValidateServerCertificate(object sender, X509Certificate certificate,
    X509Chain chain, SslPolicyErrors sslPolicyErrors)
{
    // Accept all certificates
    return true;
}