通过外部网站返回得到内网外部IP

static string GetIP()

{

Uri uri = new Uri("http://www.163.com");

System.Net.HttpWebRequest req = (System.Net.HttpWebRequest)System.Net.WebRequest.Create(uri);

req.Method = "POST";

req.ContentType = "application/x-www-form-urlencoded";

req.ContentLength = 0;

req.CookieContainer = new System.Net.CookieContainer();

req.GetRequestStream().Write(new byte [0], 0, 0);

System.Net.HttpWebResponse res = (System.Net.HttpWebResponse)(req.GetResponse());

StreamReader rs = new StreamReader(res.GetResponseStream(), System.Text.Encoding.GetEncoding("GB18030"));

string s = rs.ReadToEnd();

rs.Close();

req.Abort();

res.Close();

System.Text.RegularExpressions.Match m = System.Text.RegularExpressions.Regex.Match(s, @"IP：\[(?<IP>[0-9\.]*)\]");

if (m.Success) return m.Groups["IP"].Value;

return string.Empty;

}