.NET MAUI Android – HttpRequestException (UnknownHostException) – Unable to resolve host intermittently in production

Hi @Nancy Vo (WICLOUD CORPORATION)

Thank you for your response.

Currently, I am seeing a high number of non-fatal HttpRequestException (UnknownHostException) connection failures in Firebase Crashlytics.

There is no API server downtime, and we do not have any DNS or backend issues from our side. The APIs are working correctly.

Most of these exceptions are occurring when:

• The app is in background state
• Around 88% of the cases happen in background
• About 76% of affected devices are Samsung
• The issue flow is:
  MainActivity → Announcements → Atlas → Notifications → User(******@j.com) → LogToAzureStorage → Connection failure

Stack trace:

stack trace --- java.net.UnknownHostException: Unable to resolve host "fd-j.com-prod.azurefd.net": No address associated with hostname at java.net.Inet6AddressImpl.lookupHostByName(Inet6AddressImpl.java:124) at java.net.Inet6AddressImpl.lookupAllHostAddr(Inet6AddressImpl.java:103)

It does not impact the user experience directly, but it is increasing the number of non-fatal exceptions in Crashlytics.

I suspect this might be related to:

Android background execution limits

Samsung battery optimization / aggressive background restrictions

Network being temporarily unavailable when the app is resumed from background

Could you please help me understand:

1. Is UnknownHostException commonly triggered when the app is in background due to OS-level restrictions?
2. Can battery optimization (especially on Samsung devices) cause temporary DNS resolution failures?
3. What is the recommended way in .NET MAUI to safely handle API calls when the app is in background or resuming?

Any guidance on how to properly handle or reduce these background connection failures would be helpful.

Thank you.

Hi @nandu kathmandi ,

Thanks for your update.

1. Is UnknownHostException commonly triggered when the app is in background due to OS-level restrictions?

Yes, it can be.

If device is waking up from Doze, DNS may temporarily fail. When your app is in the background, android may put it under Doze/App Standby. In that state, background work (including network activity) can be delayed or restricted. If your app tries to call your API during that window, the very first step, DNS lookup (turning your host name into an IP) may fail, and that surfaces as UnknownHostException. (Base on Doze and App Standby)

While this is a non-Microsoft link, it is Android official documation.

2. Can battery optimization (especially on Samsung devices) cause temporary DNS resolution failures?

Indirectly but yes.

Battery optimization can contribute indirectly. It doesn’t “break DNS” itself, but aggressive power/background restrictions can increase the chance that your request runs when background networking is limited or the network isn’t ready yet, DNS lookup is often one of the first things you see fail in that situation.

3. What is the recommended way in .NET MAUI to safely handle API calls when the app is in background or resuming?

• I recommend you shouldn't let it crash the app. Instead, handle HttpRequestException as a normal failure path and don’t assume you got data back. Always check for null or failure results before trying to use the data.
• Furthermore, add a short delay before executing network requests when the app resumes. (MAUI lifecycle documentation)
• For things like LogToAzureStorage, don’t try to send immediately while backgrounded. Queue it locally and send it later when the app is active again or the network is clearly available.

Hope this helps!

Thank you for your response @Nancy Vo (WICLOUD CORPORATION) ,

As per your suggestion, can I add a small delay inside MauiProgram.cs since I am using .CreateWindow(...) during the app startup phase?

await Task.Delay(500).ConfigureAwait(false);

Also, regarding your suggestion that LogToAzureStorage(), this is my current approach.

public async Task<bool> LogToAzureStorage(IMSAuthService msAuthService, LogsTableEntity logsTableEntity)
        {
            try
            {
                HttpClient client = GetHttpClient();
                HttpContent Content = new StringContent(JsonConvert.SerializeObject(logsTableEntity), Encoding.UTF8, "application/json");
                var response = await PostAsync(client, new Uri(Configurations.BaseUrl + AppConstants.UserLogsAPI), Content);
                    response = null;
                if (response.StatusCode == System.Net.HttpStatusCode.Unauthorized)
                {
                    await msAuthService.GetApiAccessToken();

                    client = GetHttpClient();
                    response = await PostAsync(client, new Uri(Configurations.BaseUrl + AppConstants.UserLogsAPI), Content);
                }

                if (response.IsSuccessStatusCode)
                {
                    return true;
                }
            }
            catch (Exception ex)
            {
                CrashlyticsLogger.LogException("LogToAzureStorage", ex);
                return false;
            }

            return false;
        }

Can I modify it like this before call the HttpClient?

 if (Connectivity.Current.NetworkAccess != NetworkAccess.Internet)
        {
            return false; // No internet → skip API         
		}          
	await Task.Delay(1000); //Small delay before making the request

And I Always check for null or failure results before trying to use the data.

Thank you for your guidance.

Thank you for your response @Nancy Vo (WICLOUD CORPORATION) ,

As per your suggestion, can I add a small delay inside MauiProgram.cs since I am using .CreateWindow(...) during the app startup phase?

await Task.Delay(500).ConfigureAwait(false);

Also, regarding your suggestion that LogToAzureStorage(), this is my current approach.

Can I modify it like this before call the HttpClient?

 if (Connectivity.Current.NetworkAccess != NetworkAccess.Internet)
        {
            return false; // No internet → skip API         
		}          
	await Task.Delay(1000); //Small delay before making the request

And I am aways checking for null or failure results before trying to use the data.

Thank you for your guidance.

Hi @nandu kathmandi ,

Thanks for your response!

I hope this can help you further:

Can you add a small delay inside MauiProgram.cs since you are using .CreateWindow(...) during the app startup phase?

Yes you can, but I would not recommend adding a blanket delay there unless you've confirmed the failures are happening specifically during cold start. In your data, most failures happen in the background or resume path, so delaying app startup won’t reliably target the problem and will slow down every launch. I would recommend you apply the delay only around the specific network call that's vulnerable (like your LogToAzureStorage), especially after resume.

Can you modify it like this before call the HttpClient?

Yes, that’s a good approach. It helps you avoid firing the request when the OS reports there's no Internet yet and it gives the device a short moment to finish reconnecting.

Hope this helps! If my answer was helpful - kindly follow the instructions here so others with the same problem can benefit as well. Thanks for your time.