Answers

• AlmaJensen.9398 USMember ✭✭✭

  May 2018

  did you try calling the service using http instead of https?

  I haven't tried this myself but maybe it'll help.

  https://forums.xamarin.com/discussion/124695/exception-while-trying-to-connect-a-server-w-o-a-certificate

  0
• kingmathers Member ✭✭

  May 2018

  No, it requires https.

  The link you provided only covers a solution using ServicePointManager.ServerCertificateValidationCallback which is (as far as I know) not available for UWP.

  0
• kingmathers Member ✭✭

  June 2018 Accepted Answer

  In case anybody is having a similar problem: I solved this using DependecyService which implemented the Windows.Web.Http.Httpclient for UWP and the System.Net.Http.HttpClient version for Android/iOS. With this I was able to accept server certificates.

  0
• Olivetree Member ✭✭

  March 2019

  @kingmathers could you please share your code with us? I am having this issue and I am having a hard time to implement the Dependency Service you were talking about.

  Thanks.

  0
• kingmathers Member ✭✭

  March 2019 Accepted Answer

  Hello,

  I will gladly share my code. I hope you are familiar with Dependency Service, otherwise this might be complicated.

  In my Xamarin.Forms app, I use this code on all platforms:

  public interface IServerCommunication
  {
      Task<string> GetFromServerAsync(string URL);
  }   
  
  //later on, when I download the data: (URL is a provided string)
  
  string result = await DependencyService.Get<IServerCommunication>().GetFromServerAsync(URL);
  

  I implement the interface for UWP and Android different. This is for UWP:

  public async Task<string> GetFromServerAsync(string URL)
  {
      HttpClient client = await PreparedClientAsync();
  
      HttpResponseMessage response;
  
      try
      {
          response = await client.GetAsync(new Uri(URL));
  
          IBuffer buffer = await response.Content.ReadAsBufferAsync();
          DataReader reader = DataReader.FromBuffer(buffer);
          byte[] fileContent = new byte[reader.UnconsumedBufferLength];
          reader.ReadBytes(fileContent);
          string result = Encoding.UTF8.GetString(fileContent, 0, fileContent.Length);
  
          return result;
      }
      catch (Exception ex)
      {
          return "error";
      }
  }
  
  private async Task<HttpClient> PreparedClientAsync()
  {
      var filter = new Windows.Web.Http.Filters.HttpBaseProtocolFilter();
  
      filter.IgnorableServerCertificateErrors.Add(ChainValidationResult.Expired);
      filter.IgnorableServerCertificateErrors.Add(ChainValidationResult.Untrusted);
      filter.IgnorableServerCertificateErrors.Add(ChainValidationResult.InvalidName);
  
      HttpClient client = new HttpClient(filter);
  
      //I also handle other stuff here (client certificate, authentification), but the lines above should allow the Httpclient to accept all certificates
  
      return client;
  }
  

  This is for Android (should also work on iOS, but I have not tried it out):

  public async Task<string> GetFromServerAsync(string URL)
  {
      HttpClient client = PreparedClient();
  
      HttpResponseMessage response = new HttpResponseMessage();
  
      try
      {
          response = await client.GetAsync(URL);
          string result = await response.Content.ReadAsStringAsync();
          return result;
      }
      catch (Exception ex)
      {
          return "error";
      }
  }
  
  private HttpClient PreparedClient()
  {
      HttpClientHandler handler = new HttpClientHandler();
  
      //not sure about this one, but I think it should work to allow all certificates:
      handler.ServerCertificateCustomValidationCallback += (sender, cert, chaun, ssPolicyError) =>
      {
          return true;
      };
  
  
      HttpClient client = new HttpClient(handler);
  
      return client;
  }
  

  1