private async Task ReceiveMessagesAsync(CancellationToken cancellationToken)
{
var c2dReceiveExceptionsToBeIgnored = new Dictionary <Type, string>(_exceptionsToBeIgnored)
{
{ typeof(DeviceMessageLockLostException), "Attempted to complete a received message whose lock token has expired" }
};
while (!cancellationToken.IsCancellationRequested)
{
if (!IsDeviceConnected)
{
await Task.Delay(s_sleepDuration);
continue;
}
else if (_transportType == TransportType.Http1)
{
// The call to ReceiveAsync over HTTP completes immediately, rather than waiting up to the specified
// time or when a cancellation token is signaled, so if we want it to poll at the same rate, we need
// to add an explicit delay here.
await Task.Delay(s_sleepDuration);
}
_logger.LogInformation($"Device waiting for C2D messages from the hub for {s_sleepDuration}." +
$"\nUse the IoT Hub Azure Portal or Azure IoT Explorer to send a message to this device.");
await RetryOperationHelper.RetryTransientExceptionsAsync(
operationName : "ReceiveAndCompleteC2DMessage",
asyncOperation : async() => await ReceiveMessageAndCompleteAsync(),
shouldExecuteOperation : () => IsDeviceConnected,
logger : _logger,
exceptionsToBeIgnored : c2dReceiveExceptionsToBeIgnored,
cancellationToken : cancellationToken);
}
}
private async Task SendMessagesAsync(CancellationToken cancellationToken)
{
int messageCount = 0;
while (!cancellationToken.IsCancellationRequested)
{
if (IsDeviceConnected)
{
_logger.LogInformation($"Device sending message {++messageCount} to IoT hub.");
using Message message = PrepareMessage(messageCount);
await RetryOperationHelper.RetryTransientExceptionsAsync(
operationName : $"SendD2CMessage_{messageCount}",
asyncOperation : async() => await s_deviceClient.SendEventAsync(message),
shouldExecuteOperation : () => IsDeviceConnected,
logger : _logger,
exceptionsToBeIgnored : _exceptionsToBeIgnored,
cancellationToken : cancellationToken);
_logger.LogInformation($"Device sent message {messageCount} to IoT hub.");
}
await Task.Delay(s_sleepDuration);
}
}
private async Task GetTwinAndDetectChangesAsync(CancellationToken cancellationToken)
{
Twin twin = null;
// Allow a single thread to call GetTwin here
await _initSemaphore.WaitAsync(cancellationToken);
await RetryOperationHelper.RetryTransientExceptionsAsync(
operationName : "GetTwin",
asyncOperation : async() =>
{
twin = await s_deviceClient.GetTwinAsync();
_logger.LogInformation($"Device retrieving twin values: {twin.ToJson()}");
TwinCollection twinCollection = twin.Properties.Desired;
long serverDesiredPropertyVersion = twinCollection.Version;
// Check if the desired property version is outdated on the local side.
if (serverDesiredPropertyVersion > s_localDesiredPropertyVersion)
{
_logger.LogDebug($"The desired property version cached on local is changing from {s_localDesiredPropertyVersion} to {serverDesiredPropertyVersion}.");
await HandleTwinUpdateNotificationsAsync(twinCollection, cancellationToken);
}
},
shouldExecuteOperation : () => IsDeviceConnected,
logger : _logger,
exceptionsToBeIgnored : _exceptionsToBeIgnored,
cancellationToken : cancellationToken);
_initSemaphore.Release();
}
private async Task HandleTwinUpdateNotificationsAsync(TwinCollection twinUpdateRequest, object userContext)
{
CancellationToken cancellationToken = (CancellationToken)userContext;
if (!cancellationToken.IsCancellationRequested)
{
var reportedProperties = new TwinCollection();
_logger.LogInformation($"Twin property update requested: \n{twinUpdateRequest.ToJson()}");
// For the purpose of this sample, we'll blindly accept all twin property write requests.
foreach (KeyValuePair <string, object> desiredProperty in twinUpdateRequest)
{
_logger.LogInformation($"Setting property {desiredProperty.Key} to {desiredProperty.Value}.");
reportedProperties[desiredProperty.Key] = desiredProperty.Value;
}
// For the purpose of this sample, we'll blindly accept all twin property write requests.
await RetryOperationHelper.RetryTransientExceptionsAsync(
operationName : "UpdateReportedProperties",
asyncOperation : async() => await s_deviceClient.UpdateReportedPropertiesAsync(reportedProperties, cancellationToken),
shouldExecuteOperation : () => IsDeviceConnected,
logger : _logger,
exceptionsToBeIgnored : _exceptionsToBeIgnored,
cancellationToken : cancellationToken);
}
}
private async Task InitializeAndSetupClientAsync(CancellationToken cancellationToken)
{
if (ShouldClientBeInitialized(s_connectionStatus))
{
// Allow a single thread to dispose and initialize the client instance.
await _initSemaphore.WaitAsync(cancellationToken);
try
{
if (ShouldClientBeInitialized(s_connectionStatus))
{
_logger.LogDebug($"Attempting to initialize the client instance, current status={s_connectionStatus}");
// If the device client instance has been previously initialized, close and dispose it.
if (s_deviceClient != null)
{
try
{
await s_deviceClient.CloseAsync(cancellationToken);
}
catch (UnauthorizedException) { } // if the previous token is now invalid, this call may fail
s_deviceClient.Dispose();
}
s_deviceClient = DeviceClient.CreateFromConnectionString(_deviceConnectionStrings.First(), _transportType, _clientOptions);
s_deviceClient.SetConnectionStatusChangesHandler(ConnectionStatusChangeHandler);
_logger.LogDebug("Initialized the client instance.");
}
}
finally
{
_initSemaphore.Release();
}
// Force connection now.
// We have set the "shouldExecuteOperation" function to always try to open the connection.
// OpenAsync() is an idempotent call, it has the same effect if called once or multiple times on the same client.
await RetryOperationHelper.RetryTransientExceptionsAsync(
operationName : "OpenConnection",
asyncOperation : async() => await s_deviceClient.OpenAsync(cancellationToken),
shouldExecuteOperation : () => true,
logger : _logger,
exceptionsToBeIgnored : _exceptionsToBeIgnored,
cancellationToken : cancellationToken);
_logger.LogDebug($"The client instance has been opened.");
// You will need to subscribe to the client callbacks any time the client is initialized.
await RetryOperationHelper.RetryTransientExceptionsAsync(
operationName : "SubscribeTwinUpdates",
asyncOperation : async() => await s_deviceClient.SetDesiredPropertyUpdateCallbackAsync(HandleTwinUpdateNotificationsAsync, cancellationToken),
shouldExecuteOperation : () => IsDeviceConnected,
logger : _logger,
exceptionsToBeIgnored : _exceptionsToBeIgnored,
cancellationToken : cancellationToken);
_logger.LogDebug("The client has subscribed to desired property update notifications.");
}
}
