How to redeem external IP address on Android?

Question

The address IPV4 local is not something very complex to rescue, can do this using the class NetworkInterface. But beyond the site, there is also the External IP, in which I realized that some people use some Apis, as that of the Whatismyip, for the return of information concerning the network. In Whatismyip there is the free version, but very limited.

Is there a way to rescue external IP without needing an external service? If so, how could I do that? If not, what viable way to do it?

Answer 1

As explained in this reply it is not possible do this without relying on an external service:

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.

How to get IP with external services

There are several third-party services that provide this, for example:

• http://ip2country.sourceforge.net/
• http://www.whatismyip.org/
• https://wtfismyip.com
• https://ipinfo.io/ip

However they all have points in common, being a third party service can occur to many people around the world using a stop service hour, I’m not saying not to use, but it’s always good to have a fallback.

I would say that a good way would be to have a server of your own, usually mobile apps use internet, if your app will provide access to some data online for the user the best would be to check the IP at this time on the server itself, an example using Defaulthttpclient:

HttpClient client = new DefaultHttpClient();
HttpGet request = new HttpGet("http://meuservidor/api/ip");

try
{
    HttpResponse response = client.execute(request);

    //Resposta, pode ser uma String
    EntityUtils.toString(response.getEntity());
}
catch (IOException e)
{
    Log.d("error", e.getLocalizedMessage());
}

However if the application really does not have any server for whatever reason, "there is no harm" in using third party services, as long as there is at least one fallback, for example you try Service 1, if it fails because it is out of the air, you try Service 2 and so on.

In this case it would be interesting to also put a very short timeout to not seem that the application is slow, for example:

//Configura
HttpParams parameters = new BasicHttpParams();

int timeoutConnection = 2000;
HttpConnectionParams.setConnectionTimeout(parameters, timeoutConnection);

int timeoutSocket = 2000;
HttpConnectionParams.setSoTimeout(parameters, timeoutSocket);

DefaultHttpClient client = new DefaultHttpClient(parameters);

// Começa a requisição a partir daqui...
HttpGet request = new HttpGet(urlDoServico);

In general the code would look like this:

String myIp;

String[] toppings = { "http://servico1.com", "http://servico2.com", "http://servico3.com" };

//Configura
HttpParams parameters = new BasicHttpParams();

int timeoutConnection = 2000;
HttpConnectionParams.setConnectionTimeout(parameters, timeoutConnection);

int timeoutSocket = 2000;
HttpConnectionParams.setSoTimeout(parameters, timeoutSocket);

DefaultHttpClient client = new DefaultHttpClient(parameters);

// Começa a requisição a partir daqui...
HttpGet request;

final Pattern regexValidateIp = Pattern.compile("^\\d{1,3}\\.d{1,3}\\.\\d{1,3}$");

for (int i = 0; i < services.length; i++) {
    request = new HttpGet(services[i]);

    try {
        HttpResponse response = client.execute(request);

        //Pode tratar a a resposta aqui
        String resposeData = EntityUtils.toString(response.getEntity());

        if (regexValidateIp.matcher(resposeData).find()) {
             myIp = resposeData;
             break; //Finaliza o loop
        }
    } catch (IOException e) {}
}

//Exibe o IP
Log.d("IP:", myIp);

Of course it’s good to remember that some returns JSON, others return HTML, so maybe you can get the header Content-Type and check this, you can put it inside a Thread or something, since the check may take some time.