Xamarin IOS Notification HTTP Post failing - ios

Question

I have a Xamarin IOS app that uses remote notifications with actions. When an action button is pressed, I want to post a message back to the server to record the response. This is mostly working. If the app is active it always works. If the app is in the background then I am sometimes getting the following exception:
System.Net.Http.HttpRequestException: The network connection was lost. ---> Foundation.NSErrorException: Error Domain=NSURLErrorDomain Code=-1005 "The network connection was lost." UserInfo={_kCFStreamErrorCodeKey=-4, NSUnderlyingError=0x2815e27c0 {Error Domain=kCFErrorDomainCFNetwork Code=-1005 "(null)" UserInfo={NSErrorPeerAddressKey={length = 16, capacity = 16, bytes = 0x100201bb0d42d4cd0000000000000000}, _kCFStreamErrorCodeKey=-4, _kCFStreamErrorDomainKey=4}}, _NSURLErrorFailingURLSessionTaskErrorKey=LocalDataTask <8A9B9110-D44C-46F5-B67E-B11231D82319>.<18>, _NSURLErrorRelatedURLSessionTaskErrorKey=(
"LocalDataTask <8A9B9110-D44C-46F5-B67E-B11231D82319>.<18>"
), NSLocalizedDescription=The network connection was lost., NSErrorFailingURLStringKey=https://callservice-v2.azurewebsites.net/api/callaction, NSErrorFailingURLKey=https://callservice-v2.azurewebsites.net/api/callaction, _kCFStreamErrorDomainKey=4}
--- End of inner exception stack trace ---
at System.Net.Http.NSUrlSessionHandler.SendAsync (System.Net.Http.HttpRequestMessage request, System.Threading.CancellationToken cancellationToken) <0x105b568a0 + 0x009a3> in :0
at System.Net.Http.HttpClient.FinishSendAsyncBuffered (System.Threading.Tasks.Task`1[TResult] sendTask, System.Net.Http.HttpRequestMessage request, System.Threading.CancellationTokenSource cts, System.Boolean disposeCts) <0x105a960c0 + 0x005f4> in <692b89da4aac4c12a3ac3af90678ac25#21125a282fd7860e37414196dba0c548>:0
at Dialer.Models.HttpDataServerClient.PostAsync (System.String api, System.Object message) <0x105f01a70 + 0x0047b> in <8e7629d69d3341bfa512d35c83fa84e0#21125a282fd7860e37414196dba0c548>:0
I have a UNUserNotificationCenterDelegate that has the following method:
public override void DidReceiveNotificationResponse(UNUserNotificationCenter center, UNNotificationResponse response, Action completionHandler)
{
try
{
_logger.TraceInfo($"DidReceiveNotificationReponse entered");
var userInfo = response.Notification.Request.Content.UserInfo;
var token = GetUserInfoItem(userInfo, "CallToken");
var subscriberPhoneNumber = GetUserInfoItem(userInfo, "SubscriberPhoneNumber");
var clientCallingNumber = GetUserInfoItem(userInfo, "ClientCallingNumber");
var clientDialedNumber = GetUserInfoItem(userInfo, "ClientDialedNumber");
_logger.TraceInfo($"Notification received, action: {response.ActionIdentifier}, token: {token}, phone #: {subscriberPhoneNumber}");
// Take action based on Action ID
switch (response.ActionIdentifier)
{
case "accept-call":
_callActionsHandler.SendAction(token, subscriberPhoneNumber, CallActions.Accept);
break;
case "send-to-voice-mail":
_callActionsHandler.SendAction(token, subscriberPhoneNumber, CallActions.VoiceMail);
break;
}
// Save the incoming call in the call history
_callHistoryAccess.AddCallToHistory(
new CallHistoryInstance()
{
CallerIdNumber = clientDialedNumber,
CallTime = DateTime.UtcNow,
CustomerPhoneNumber = clientCallingNumber,
Type = CallHistoryInstance.CallType.Inbound
});
}
catch (Exception ex)
{
_logger.TraceException($"An exception occurred while processing the notification", ex);
}
// Inform caller it has been handled
completionHandler();
}
The important thing here is the _callActionsHandler.SendAction call. That code is here:
public void SendAction(string callToken, string subscriberPhoneNumber, CallActions action)
{
Task.Run(async () =>
{
await SendActionAsync(new CallActionMessage(subscriberPhoneNumber, action, callToken));
});
}
private async Task SendActionAsync(CallActionMessage msg)
{
_logger.TraceInfo($"Registering call action for {msg.CallToken} to {msg.CallAction}");
var result = await _client.PostAsync(Constants.CallActionsApi, msg);
if (result != 200)
{
throw new CallActionsException($"HTTP status {result}");
}
}
This code has a wrapper around HttpClient. The PostAsync method is here:
public async Task<int> PostAsync(string api, object message)
{
var apiUrl = Constants.DefaultAppApi + api;
var contentText = JsonConvert.SerializeObject(message);
var content = new StringContent(contentText, Encoding.UTF8, "application/json");
var backOff = 10;
var retryCount = 5;
HttpResponseMessage response = null;
for (var attempt = 1; attempt <= retryCount; attempt++)
{
_logger.TraceInfo($"DataServerClient Post message: {message.GetType().Name}, attempt = {attempt}");
try
{
response = await _client.PostAsync(apiUrl, content);
}
catch (Exception ex)
{
if (attempt == retryCount)
_logger.TraceException($"DataServerClient Post failed", ex);
}
if (response != null && response.IsSuccessStatusCode)
{
_logger.TraceInfo($"DataServerClient post was successful at retry count: {attempt}");
break;
}
backOff *= 2;
await Task.Delay(backOff);
}
return (int)response.StatusCode;
}
I suspected an issue with the await and possibly needing a ConfigureAwait(). I have experimented with both ConfigureAwait(true) and ConfigureAwait(false) with no success. The results are very similar.
I am at a loss right now for why this is failing. Can anyone provide some information here why this is failing? Or, does anyone have code that does an HTTP post in response to a notification action?