C# 取得 機器 廣域/真實/實際 IP (Global IP/public ip/external ip address)

資料來源: https://www.c-sharpcorner.com/blogs/how-to-get-public-ip-address-using-c-sharp1

https://www.c-sharpcorner.com/blogs/how-to-get-public-ip-address-using-c-sharp1

https://codingvision.net/c-how-to-get-external-ip-address

code

        public static string GetPublicIPAddress(int mode=0)
        {
            //https://www.c-sharpcorner.com/blogs/how-to-get-public-ip-address-using-c-sharp1
            //https://www.codegrepper.com/code-examples/csharp/c%23+get+public+ip+address
            //https://codingvision.net/c-how-to-get-external-ip-address
            String address = "";
            switch(mode)
            {
                case 0:
                    using (WebClient client = new WebClient())
                    {
                        address = client.DownloadString("https://api.ipify.org/");
                    }
                    break;
                case 2:
                    address = new WebClient().DownloadString(@"http://icanhazip.com").Trim();
                    break;
                case 1:
                    WebRequest request = WebRequest.Create("http://checkip.dyndns.org/");
                    using (WebResponse response = request.GetResponse())
                    using (StreamReader stream = new StreamReader(response.GetResponseStream()))
                    {
                        address = stream.ReadToEnd();
                    }

                    int first = address.IndexOf("Address: ") + 9;
                    int last = address.LastIndexOf("</body>");
                    address = address.Substring(first, last - first);
                    break;
            }

            return address;
        }