获取外网访问者的真实ip，在线等待
HttpWebRequest req = (HttpWebRequest)HttpWebRequest.Create("http://www.ip138.com/ip2city.asp");
  req.Method = "POST";
  req.ContentType = "application/x-www-form-urlencoded";
  req.ContentLength = 0;
  req.CookieContainer = new CookieContainer();
  req.GetRequestStream().Write(new byte[0], 0, 0);
  WebResponse res = req.GetResponse();
  StreamReader rs = new StreamReader(res.GetResponseStream(), Encoding.GetEncoding("gb2312"));
  string s = rs.ReadToEnd();
  rs.Close();
  req.Abort();
  res.Close();
  Match m = Regex.Match(s, @"(\d+)\.(\d+)\.(\d+)\.(\d+)");

  string ipHost = string.Empty;



到这 WebResponse res = req.GetResponse();一步报远（程服务器返回错误: (403) 已禁止。）求解

------解决方案--------------------
参考1：

C# code

string GetInternalIpAddress1()
        {
            try
            {
                string strUrl = "http://www.3322.org/dyndns/getip"; //获得IP的网址了   
                Uri uri = new Uri(strUrl);
                WebRequest wr = WebRequest.Create(uri);
                Stream s = wr.GetResponse().GetResponseStream();
                StreamReader sr = new StreamReader(s, Encoding.Default);
                string all = sr.ReadToEnd(); //读取网站的数据   
                all = all.Replace("\r\n", "");
                return all;
            }
            catch (Exception ex)
            {
                return "";
            }
        }