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hello I am trying to launch an intent with a webview from a user entered URL, I have been looking everywhere online and I can't find a concrete answer as to how to make sure the website will actually connect before allowing the user to proceed to the next activity. I have found many tools to make sure the URL follows the correct format but none that actually let me make sure it can actually connect.

Johan Sebastian Ospina
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    Use a `GET` request and check for an appropriate response code. – Malik Brahimi Jun 16 '15 at 14:53
  • I googled `java check if website is up` and got lots of useful results. What have you tried? Are you using java or c#? Not both, I presume. – tnw Jun 16 '15 at 14:54
  • Just try HEAD request, and have a look at the response code. GET will get you the whole document, HEAD only metadata. In the same session you can't try HEAD, and if positive do GET while proceed to your next activity, if negative show some error message or what ever. – Jean-Baptiste Yunès Jun 16 '15 at 14:59

5 Answers5

3

You can use WebClient and check if any exception is thrown:

using (var client = new HeadOnlyClient())
{
    try
    {
        client.DownloadString("http://google.com");
    }
    catch (Exception ex)
    {
        // URL is not accessible.
    }
}

You can catch more specific exceptions to make it more elegant.

You can also use custom modification to WebClient to check HEAD only and decrease the amount of data downloaded:

class HeadOnlyClient : WebClient
{
    protected override WebRequest GetWebRequest(Uri address)
    {
        WebRequest req = base.GetWebRequest(address);
        req.Method = "HEAD";
        return req;
    }
}
Przemysław Ładyński
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0

I would suggest you to use HttpHead for simple request with AndroidHttpClient, but it is deprecated now. You can try to implement HEAD Request by sockets.

Iliiaz Akhmedov
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0

You can try to ping the address first.

See this SO question: How to Ping External IP from Java Android

Community
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zaph89
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0

Another option: Connectivity Plugin for Xamarin and Windows

Task<bool> IsReachable(string host, int msTimeout = 5000);

But, any pre-check that succeeds isn't guaranteed as the very next request might fail so you should still handle that.

Derek Beattie
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0

Here's what I ended up doing to Check if a Host name is reachable. I was connecting to a site with a self signed certificate so that's why I have the delegate in the ServiceCertificateValidationCallback. 

private async Task<bool> CheckHostConnectionAsync (string serverName)
    {

        string Message = string.Empty;
        HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(serverName);

        ServicePointManager.ServerCertificateValidationCallback += delegate 
        {
            return true;
        };

        // Set the credentials to the current user account
        request.Credentials = System.Net.CredentialCache.DefaultCredentials;
        request.Method = "GET";
        request.Timeout = 1000 * 40; 


        try
        {
            using (HttpWebResponse response =  (HttpWebResponse) await request.GetResponseAsync ())
            {
                      // Do nothing; we're only testing to see if we can get the response
            }
        }
        catch (WebException ex)
        {
            Message += ((Message.Length > 0) ? "\n" : "") + ex.Message;
            return false;
        }


        if (Message.Length == 0) 
        {
            goToMainActivity (serverName);
        }
        return true; 

    }
Johan Sebastian Ospina
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