void SendHttpError(string ErrorCodeAndReason)
{
string html_body = "<html>\n <body>\n <h1>" +
ErrorCodeAndReason + "</h1>\n </body>\n</html>";
WriteBinary(System.Text.Encoding.ASCII.GetBytes(
"HTTP/1.0 " + ErrorCodeAndReason + "\r\n" +
"Connection: close\r\n" +
"Content-Length: " + html_body.Length + "\r\n" +
"\r\n" + html_body + "\r\n"));
}