sslStream.Read问题：读取的所有字节均为0

TcpClient client = new TcpClient(\"69.147.112.160\", 443);
SslStream sslStream = new SslStream(client.GetStream(),false,
                                    ValidateServerCertificate,null);
try
{
    sslStream.AuthenticateAsClient(\"mail.yahoo.com\");
}
catch (AuthenticationException e)
{

    return;
}
byte[] messsage = Encoding.UTF8.GetBytes(\".<EOF>\");
sslStream.Write(messsage);
sslStream.Flush();
byte[] buffer = new byte[4096];
int bytes2 = -1;
do
{
    /**************************************************
     *** JUST A LINE BELOW ALL buffer BYTES ARE ZERO!**
     *************************************************/

    bytes2 = sslStream.Read(buffer, 0, 4096);
    m_sockClient.Send(buffer, bytes2, 0);
} while (bytes != 0);