How can I inspect my Xamarin.Forms app's network traffic?

TheGabeChavezTheGabeChavez USMember, University
edited September 2014 in Xamarin.Forms

I have an async method that calls a web service thus (I've omitted some boilerplate stuff):

var client = new HttpClient(new NativeMessageHandler());
client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));  
var response = await client.SendAsync(httpRequest);
var jsonString = await response.Content.ReadAsStringAsync();

I know the client.SendAsync() call is successfully connecting to my service, but the requests aren't being picked up by Fiddler.

I want to inspect the request and response headers but Fiddler isn't recording any traffic from my app. I'm using Genymotion emulation, and I've configured the emulator to use the Fiddler proxy ( successfully. If I use the emulator browser to browse the web, the requests appear in the traffic list, yet none of my app's traffic does.

Does anyone have any insight regarding this?



  • JPBoroJPBoro PHMember ✭✭
    edited September 2014

    Fiddler interferes with the simulator's network connection on our end. So what we do is we attach the iOS and Android device on the Mac and PC, run the app on the device, ( then for iOS, we disconnect the iphone from the Mac then attach it on the PC), then turn on fiddler. Make sure you follow Telerik's docs: (iOS) , (Android) .

    Also, when you're done, set back your the WI-FI proxy on your device to 'Auto' or else your app or device won't connect to the internet when you disconnecte from the PC.

  • TheGabeChavezTheGabeChavez USMember, University

    Thanks for replying JP, but what I'm looking for is a way to debug from visual studio and simultaneously view network traffic in fiddler. I've tried a lot of things, including trying to reconfigure the network settings in Virtual Box, but all I managed to do was make Genymotion unusable :(

  • Would love to know if someone found a solution to make Fiddler working on Windows.

  • LGMaestrelliLGMaestrelli BRMember ✭✭✭

    Anyone tried monitoring on VisualStudio 2015?

    I'm still using the 2013...

  • KamilKuza.8560KamilKuza.8560 USMember, University

    Doesn't appear to be available in VS1015. I tried for iOS, Droid and WinPhone8.

  • FelixCollinsFelixCollins NZMember

    I might have a solution.

    So I had a massive struggle with this yesterday believing that it must be possible.

    So, how to do it?

    First you should do this:

    This is helpful to set up for the next step but unfortunately that won't let you see your apps traffic. The reason is that what you have done is set up a default proxy for the emulator but the app won't use it. That will be useful if you want to see other http traffic such as browser traffic from the emulator.

    Next you will have to create a proxy for the app to use. Usually it would look something like this for web requests:

    WebRequest.DefaultWebProxy = new WebProxy();

    or for httpclient

    var handler = new HttpClientHandler{Proxy = new WebProxy(uri)};

    Unfortunately some xamarin profiles won't have access to web proxy so we'll have to make our own. The most important thing is that we implement IWebProxy. You can use this:

    public class Proxy : System.Net.IWebProxy
            public System.Net.ICredentials Credentials
            private readonly Uri _proxyUri;
            public Proxy(Uri proxyUri)
                _proxyUri = proxyUri;
            public Uri GetProxy(Uri destination)
                return _proxyUri;
            public bool IsBypassed(Uri host)
                return false;

    Now that we have a proxy class we need a uri which we make using the ip and port from fiddler which we found in the above article:

    var uri = new Uri("http://{fiddlerIP}:{fiddlerPort}/");

    Then we can use this for WebRequest:

    WebRequest.DefaultWebProxy = new Proxy();

    or for HttpClient:
    var handler = new HttpClientHandler
    Proxy = new Proxy(uri)
    var httpClient = new HttpClient(handler);

    I hope this helps!

    PS. This editor is constantly suggesting smileys to me and I can't fix this last code block :neutral:

  • DavidDancyDavidDancy AUMember ✭✭✭✭

    On iOS at least there's NSURLProtocol which can intercept network requests as they are being made. It's extremely powerful and really not hard to use.

    Of course this only works if you're using the NSURLConnection or NSURLSession classes on iOS, or if you've got ModernHttpClient or the latest shiny networking from Xamarin.

    I don't know if there's an equivalent on Android.

Sign In or Register to comment.