Recover External IP without third party services

Question

I have a WPF application. I need to know the external IP of the machine running this application.

I found some tutorials that teach to do this through the method DownloadString() class WebClient consuming some services such as dyndns.org, icanhazip.com, finally several services.

It would be something like that:

string meuIp = new WebClient().DownloadString("http://icanhazip.com");  

To use such services I need to implement the query in at least two or three to ensure a contingency in case some service stops working or is discontinued.

Does anyone know if it is possible to do this natively with . Net Framework without using third-party services?

Answer 1

[...] you can do this natively with . Net Framework without using third party services?

No, it is not possible. Your machine has access to local IP only, provided by the internal DNS service or set manually.

The external IP is, in most of the times, the one provided by your provider for you to be accessible via NAT (Network address Translation), as in the image below:

^{NAT categorization According to RFC, Wikipedia}

In this case you will always need an external service that tells you, from his point of view, with which IP you are connecting.

Answer 2

You can use the IP Public Knowledge.

install the Nuget package:

Install-Package Ippublicknowledge

An example of use would be this:

var ip = IPK.GetMyPublicIp();
var IPinfo = IPK.GetIpInfo(ip);
    
Console.WriteLine("IP Publico: " + IPinfo.IP);
Console.WriteLine("ISP: " + IPinfo.isp);
Console.WriteLine("País: " + IPinfo.country);

Another way, as you said yourself, would be to use some external site, for example:

public static void Main(string[] args)
{
    string externalip = new WebClient().DownloadString("https://api.ipify.org");            
    Console.WriteLine(externalip);
}

In that case, this answer shows more examples to ensure contingency.

If you would like other examples, this answer has several ways to do this, including one of how to create your own Http Server for this.