// The following method is invoked by the RemoteCertificateValidationDelegate.
  public static bool ValidateServerCertificate(
        object sender,
        X509Certificate certificate,
        X509Chain chain,
        SslPolicyErrors sslPolicyErrors)
  {
     if (sslPolicyErrors == SslPolicyErrors.None)
          return true;

      Console.WriteLine("Certificate error: {0}", sslPolicyErrors);
      
      // Do not allow this client to communicate with unauthenticated servers.
      return false;
  }

// Create a TCP/IP client socket.
// machineName is the host running the server application.
TcpClient client = new TcpClient(machineName,443);
Console.WriteLine("Client connected.");
// Create an SSL stream that will close the client's stream.
SslStream sslStream = new SslStream(
    client.GetStream(), 
    false, 
    new RemoteCertificateValidationCallback (ValidateServerCertificate), 
    null
    );
// The server name must match the name on the server certificate.
try 
{
    sslStream.AuthenticateAsClient(serverName);
} 
catch (AuthenticationException e)
{
    Console.WriteLine("Exception: {0}", e.Message);
    if (e.InnerException != null)
    {
        Console.WriteLine("Inner exception: {0}", e.InnerException.Message);
    }
    Console.WriteLine ("Authentication failed - closing the connection.");
    client.Close();
    return;
}