.NET (C#) simple smartwhois class

/*
********************************************************************************************
using System;

namespace whois
{
    class Program
    {
        static int Main(string[] args)
        {
            int rc = 0;
            WhoisClient wh;
            string result;

            if (args.Length < 1)
            {
                Console.WriteLine("usage: whois <host_or_ip>");
                return 1;
            }


            wh = new WhoisClient();
            result = wh.Whois(args[0]);
            if (!string.IsNullOrEmpty(wh.errMsg))
            {
                Console.WriteLine(string.Format("# ERR: {0}", wh.errMsg));
                rc = 2;
            }
            if (string.IsNullOrEmpty(result))
            {
                return 3;
            }
            Console.WriteLine(string.Format("# {0} :: {1}", wh.srvName, args[0]));
            Console.Write(result);
            return rc;
        }
    }
}
********************************************************************************************
*/


using System;
using System.IO;
using System.Net.Sockets;
using System.Text;

namespace whois
{
    class WhoisClient
    {
        #region privatedata
        private const int    WHOIS_PORT = 43;
        private const string BASE_WHOIS = "whois.iana.org";
        private const string TAG_SINGLE = "to single out one record";
        private const string TAG_DOMAIN = "domain name: {0}";
        private const string TAG_REDIR  = "whois server:";
        private const string TAG_HINT   = "whois:";

        private string      _lastErrMsg = null;
        private string      _lastServer = null;
        #endregion

        #region instance
        /// <summary>
        /// instance the class
        /// </summary>
        public WhoisClient()
        {
            _lastErrMsg = null;
            _lastServer = null;
        }
        #endregion

        #region properties
        /// <summary>
        /// returns last error message
        /// </summary>
        public string errMsg
        {
            get { return _lastErrMsg; }
        }

        /// <summary>
        /// returns last whois server name
        /// </summary>
        public string srvName
        {
            get { return _lastServer; }
        }

        #endregion

        #region methods
        /// <summary>
        /// run a whois query
        /// </summary>
        /// <param name="query">query string (IP or domain name)</param>
        /// <param name="server">optional: server name or address</param>
        /// <param name="port">optional: server port</param>
        /// <returns>the whois lookup result or null</returns>
        public string Whois(string query, string server = "", int port = WHOIS_PORT)
        {
            string srv = server;

            if (string.IsNullOrEmpty(srv))
            {
                srv = getServer(query);
                if (string.IsNullOrEmpty(srv)) return null;
            }

            string result = QuerySrv(query, srv, port);
            string single = refineQuery(result, query);
            if (!string.IsNullOrEmpty(single))
            {
                result = QuerySrv(single, srv, port);
                if (!string.IsNullOrEmpty(result))
                {
                    string patt = string.Format(TAG_DOMAIN, query.ToLower());
                    int pos = result.ToLower().IndexOf(patt);
                    if (pos > 0)
                    {
                        result = result.Substring(pos);
                    }
                }
            }
            if (!string.IsNullOrEmpty(result))
            {
                string hint = getHint(result, TAG_REDIR);
                if (!string.IsNullOrEmpty(hint))
                {
                    result = QuerySrv(query, hint, port);
                }
            }
            return result;
        }
        #endregion

        #region privatecode
        /// <summary>
        /// retrieves the whois server to use for a given query
        /// </summary>
        /// <param name="query">query string</param>
        /// <returns>server name or null</returns>
        private string getServer(string query)
        {
            string buff = QuerySrv(query, BASE_WHOIS, WHOIS_PORT);
            if (string.IsNullOrEmpty(buff)) return null;
            string srv = getHint(buff, TAG_HINT);
            return srv;
        }

        /// <summary>
        /// returns the hint/redirection for a query
        /// </summary>
        /// <param name="data">query result data</param>
        /// <param name="tag">redirect tag to search</param>
        /// <returns>redirect server name or null</returns>
        private string getHint(string data, string tag)
        {
            string buf = data.ToLower();
            int pos = buf.IndexOf(tag);
            if (pos < 1) return null;
            buf = buf.Substring(pos + tag.Length);
            pos = buf.IndexOf("\n");
            if (pos < 1) return null;
            buf = buf.Substring(0, pos).Trim();
            return buf;
        }

        /// <summary>
        /// checks if query result contains multiple entries
        /// </summary>
        /// <param name="data">query result</param>
        /// <param name="query">query string</param>
        /// <returns>query refinement string or null</returns>
        private string refineQuery(string data, string query)
        {
            string buf = data.ToLower();
            int pos = buf.IndexOf(TAG_SINGLE);
            if (pos < 1) return null;
            return "=" + query.ToUpper();
        }

        /// <summary>
        /// issues a whois query to the given server
        /// </summary>
        /// <param name="query">query string</param>
        /// <param name="server">server name or ip</param>
        /// <param name="port">server port</param>
        /// <returns>query result or null</returns>
        private string QuerySrv(string query, string server, int port = 43)
        {
            string result = null;

            //  Console.WriteLine(string.Format("# querying {0}:{1} for {2}", server, port, query));
            _lastServer = server;

            try
            {
                Encoding enc = Encoding.ASCII;
                TcpClient sock = new TcpClient(server, port);
                using (Stream s = sock.GetStream())
                {
                    byte[] qry = enc.GetBytes(query + "\r\n");
                    byte[] buf = new byte[8192];
                    StringBuilder resp = new StringBuilder();
                    s.Write(qry, 0, qry.Length);
                    int nbytes = 0;
                    do
                    {
                        nbytes = s.Read(buf, 0, buf.Length);
                        if (nbytes > 0)
                        {
                            resp.Append(enc.GetString(buf, 0, nbytes));
                        }
                    } while (nbytes > 0);
                    result = resp.ToString();
                }
                sock.Close();
            }
            catch (Exception ex)
            {
                _lastErrMsg = string.Format("QuerySrv(\"{0}\",\"{1}\",{2}) :: {3}", query, server, port, ex.Message);
                result = null;
            }

            return result;
        }
        #endregion

    }
}