int main(void)
{
    IOTHUB_CLIENT_TRANSPORT_PROVIDER protocol;
    IOTHUB_MESSAGE_HANDLE message_handle;
    const char* telemetry_msg = "test_message";
    char *cert_string = NULL;

    printf("This sample will send %d messages and wait for any C2D messages.\r\nPress the enter key to end the sample\r\n\r\n", MESSAGE_COUNT);

    // Select the Protocol to use with the connection
#ifdef SAMPLE_MQTT
    protocol = MQTT_Protocol;
#endif // SAMPLE_MQTT
#ifdef SAMPLE_MQTT_OVER_WEBSOCKETS
    protocol = MQTT_WebSocket_Protocol;
#endif // SAMPLE_MQTT_OVER_WEBSOCKETS
#ifdef SAMPLE_AMQP
    protocol = AMQP_Protocol;
#endif // SAMPLE_AMQP
#ifdef SAMPLE_AMQP_OVER_WEBSOCKETS
    protocol = AMQP_Protocol_over_WebSocketsTls;
#endif // SAMPLE_AMQP_OVER_WEBSOCKETS
#ifdef SAMPLE_HTTP
    protocol = HTTP_Protocol;
#endif // SAMPLE_HTTP

    IOTHUB_DEVICE_CLIENT_HANDLE device_handle;

    // Used to initialize IoTHub SDK subsystem
    (void)IoTHub_Init();

    (void)printf("Creating IoTHub handle\r\n");
    // Create the iothub handle here
    device_handle = IoTHubDeviceClient_CreateFromConnectionString(connectionString, protocol);
    if (device_handle == NULL)
    {
        (void)printf("Failure creating device client handle.  Hint: Check you connection string.\r\n");
    }
    else
    {
        // Setting message callback to get C2D messages
        (void)IoTHubDeviceClient_SetMessageCallback(device_handle, receive_msg_callback, NULL);
        // Setting connection status callback to get indication of connection to iothub
        (void)IoTHubDeviceClient_SetConnectionStatusCallback(device_handle, connection_status_callback, NULL);

        // Set any option that are necessary.
        // For available options please see the iothub_sdk_options.md documentation

        // Turn tracing on/off
        // bool traceOn = true;
        // (void)IoTHubDeviceClient_SetOption(device_handle, OPTION_LOG_TRACE, &traceOn);

        // Provide the Azure IoT device client with the Edge root
        // X509 CA certificate that was used to setup the Edge runtime
        cert_string = obtain_edge_ca_certificate();
        (void)IoTHubDeviceClient_SetOption(device_handle, OPTION_TRUSTED_CERT, cert_string);

#if defined SAMPLE_MQTT || defined SAMPLE_MQTT_OVER_WEBSOCKETS
        //Setting the auto URL Encoder (recommended for MQTT). Please use this option unless
        //you are URL Encoding inputs yourself.
        //ONLY valid for use with MQTT
        //bool urlEncodeOn = true;
        //(void)IoTHubDeviceClient_SetOption(device_handle, OPTION_AUTO_URL_ENCODE_DECODE, &urlEncodeOn);
#endif

        for (size_t index = 0; index < MESSAGE_COUNT; index++)
        {
            // Construct the iothub message from a string
            message_handle = IoTHubMessage_CreateFromString(telemetry_msg);

            // Set Message property
            (void)IoTHubMessage_SetMessageId(message_handle, "MSG_ID");
            (void)IoTHubMessage_SetCorrelationId(message_handle, "CORE_ID");
            (void)IoTHubMessage_SetContentTypeSystemProperty(message_handle, "application%2fjson");
            (void)IoTHubMessage_SetContentEncodingSystemProperty(message_handle, "utf-8");

            // Add custom properties to message
            (void)IoTHubMessage_SetProperty(message_handle, "property_key", "property_value");

            (void)printf("Sending message %d to Edge Hub\r\n", (int)(index + 1));
            IoTHubDeviceClient_SendEventAsync(device_handle, message_handle, send_confirm_callback, NULL);

            // The message is copied to the sdk so the we can destroy it
            IoTHubMessage_Destroy(message_handle);
        }

        printf("\r\nPress any key to continue\r\n");
        (void)getchar();

        // Clean up the iothub sdk handle
        IoTHubDeviceClient_Destroy(device_handle);

        if (cert_string != NULL)
        {
            free(cert_string);
            cert_string = NULL;
        }
    }
    // Free all the sdk subsystem
    IoTHub_Deinit();

    return 0;
}
static void RecvMessage(IOTHUB_PROVISIONED_DEVICE* deviceToUse)
{
    // arrange
    IOTHUB_CLIENT_HANDLE iotHubClientHandle;

    IOTHUB_SERVICE_CLIENT_AUTH_HANDLE iotHubServiceClientHandle;
    IOTHUB_MESSAGING_CLIENT_HANDLE iotHubMessagingHandle;
    IOTHUB_MESSAGING_RESULT iotHubMessagingResult;
    IOTHUB_MESSAGE_RESULT iotHubMessageResult;

    EXPECTED_RECEIVE_DATA* receiveUserContext;
    IOTHUB_MESSAGE_HANDLE messageHandle;

    // act
    IoTHub_Init();

    // Create Service Client
    iotHubServiceClientHandle = IoTHubServiceClientAuth_CreateFromConnectionString(IoTHubAccount_GetIoTHubConnString(g_iothubAcctInfo1));
    ASSERT_IS_NOT_NULL(iotHubServiceClientHandle, "Could not initialize IoTHubServiceClient to send C2D messages to the device");

    iotHubMessagingHandle = IoTHubMessaging_Create(iotHubServiceClientHandle);
    ASSERT_IS_NOT_NULL(iotHubMessagingHandle, "Could not initialize IoTHubMessaging to send C2D messages to the device");

    iotHubMessagingResult = IoTHubMessaging_Open(iotHubMessagingHandle, openCompleteCallback, (void*)"Context string for open");
    ASSERT_ARE_EQUAL(int, IOTHUB_MESSAGING_OK, iotHubMessagingResult);

    // Create user context and message
    receiveUserContext = ReceiveUserContext_Create();
    ASSERT_IS_NOT_NULL(receiveUserContext, "Could not create receive user context");

    messageHandle = IoTHubMessage_CreateFromString(MSG_CONTENT1);

    ASSERT_IS_NOT_NULL(messageHandle, "Could not create IoTHubMessage to send C2D messages to the device");

    iotHubMessageResult = IoTHubMessage_SetMessageId(messageHandle, MSG_ID1);
    ASSERT_ARE_EQUAL(int, IOTHUB_MESSAGING_OK, iotHubMessageResult);

    iotHubMessageResult = IoTHubMessage_SetCorrelationId(messageHandle, MSG_CORRELATION_ID1);
    ASSERT_ARE_EQUAL(int, IOTHUB_MESSAGING_OK, iotHubMessageResult);

    MAP_HANDLE mapHandle = IoTHubMessage_Properties(messageHandle);
    for (size_t i = 0; i < MSG_PROP_COUNT; i++)
    {
        if (Map_AddOrUpdate(mapHandle, MSG_PROP_KEYS[i], MSG_PROP_VALS[i]) != MAP_OK)
        {
            (void)printf("ERROR: Map_AddOrUpdate failed for property %zu!\r\n", i);
        }
    }

    iotHubMessagingResult = IoTHubMessaging_SendAsync(iotHubMessagingHandle, deviceToUse->deviceId, messageHandle, sendCompleteCallback, receiveUserContext);
    ASSERT_ARE_EQUAL(int, IOTHUB_MESSAGING_OK, iotHubMessagingResult, "IoTHubMessaging_SendAsync failed, could not send C2D message to the device");
    iotHubClientHandle = IoTHubClient_CreateFromConnectionString(deviceToUse->connectionString, HTTP_Protocol);
    ASSERT_IS_NOT_NULL(iotHubClientHandle, "Failure creating Iothub Client");

    if (deviceToUse->howToCreate == IOTHUB_ACCOUNT_AUTH_X509) {
        IOTHUB_CLIENT_RESULT result;
        result = IoTHubClient_SetOption(iotHubClientHandle, OPTION_X509_CERT, deviceToUse->certificate);
        ASSERT_ARE_EQUAL(IOTHUB_CLIENT_RESULT, IOTHUB_CLIENT_OK, result, "Could not set the device x509 certificate");
        result = IoTHubClient_SetOption(iotHubClientHandle, OPTION_X509_PRIVATE_KEY, deviceToUse->primaryAuthentication);
        ASSERT_ARE_EQUAL(IOTHUB_CLIENT_RESULT, IOTHUB_CLIENT_OK, result, "Could not set the device x509 privateKey");
    }

    IOTHUB_CLIENT_RESULT result = IoTHubClient_SetMessageCallback(iotHubClientHandle, ReceiveMessageCallback, receiveUserContext);
    ASSERT_ARE_EQUAL(IOTHUB_CLIENT_RESULT, IOTHUB_CLIENT_OK, result, "Failure setting message callback");

    unsigned int minimumPollingTime = 1; /*because it should not wait*/
    if (IoTHubClient_SetOption(iotHubClientHandle, OPTION_MIN_POLLING_TIME, &minimumPollingTime) != IOTHUB_CLIENT_OK)
    {
        printf("failure to set option \"MinimumPollingTime\"\r\n");
    }

    time_t beginOperation, nowTime;
    beginOperation = time(NULL);
    while (
        (
        (nowTime = time(NULL)),
            (difftime(nowTime, beginOperation) < MAX_CLOUD_TRAVEL_TIME) //time box
            )
        )
    {
        if (Lock(receiveUserContext->lock) != LOCK_OK)
        {
            ASSERT_FAIL("unable ot lock");
        }
        else
        {
            if (receiveUserContext->wasFound)
            {
                (void)Unlock(receiveUserContext->lock);
                break;
            }
            (void)Unlock(receiveUserContext->lock);
        }
        ThreadAPI_Sleep(100);
    }

    // assert
    ASSERT_IS_TRUE(receiveUserContext->wasFound, "Failure retrieving message that was sent to IotHub."); // was found is written by the callback...

    // cleanup
    IoTHubMessage_Destroy(messageHandle);
    IoTHubMessaging_Close(iotHubMessagingHandle);
    IoTHubMessaging_Destroy(iotHubMessagingHandle);
    IoTHubServiceClientAuth_Destroy(iotHubServiceClientHandle);

    IoTHubClient_Destroy(iotHubClientHandle);
    ReceiveUserContext_Destroy(receiveUserContext);
}
void iothub_messaging_ll_sample_run(void)
{
    xlogging_set_log_function(consolelogger_log);

    if (platform_init() != 0)
    {
        (void)printf("Failed to initialize the platform.\r\n");
    }
    else
    {
        (void)printf("Calling IoTHubServiceClientAuth_CreateFromConnectionString with connection string\n");
        iotHubServiceClientHandle = IoTHubServiceClientAuth_CreateFromConnectionString(connectionString);
        if (iotHubServiceClientHandle == NULL)
        {
            (void)printf("IoTHubServiceClientAuth_CreateFromConnectionString failed\n");
        }
        else
        {
            (void)printf("Service Client Authentication handle has been created successfully\n");

            (void)printf("Creating Messaging...\n");
            iotHubMessagingHandle = IoTHubMessaging_LL_Create(iotHubServiceClientHandle);
            if (iotHubMessagingHandle == NULL)
            {
                (void)printf("IoTHubMessaging_LL_Create failed\n");
            }
            else
            {
                (void)printf("Messaging has been created successfully\n");
                (void)printf("Opening Messaging...\n");

                iotHubMessagingResult = IoTHubMessaging_LL_SetFeedbackMessageCallback(iotHubMessagingHandle, feedbackReceivedCallback, "Context string for feedback");
                if (iotHubMessagingResult != IOTHUB_MESSAGING_OK)
                {
                    (void)printf("IoTHubMessaging_LL_SetFeedbackMessageCallback failed\n");
                }
                else
                {
                    iotHubMessagingResult = IoTHubMessaging_LL_Open(iotHubMessagingHandle, openCompleteCallback, "Context string for open");
                    if (iotHubMessagingResult != IOTHUB_MESSAGING_OK)
                    {
                        (void)printf("IoTHubMessaging_LL_Open failed\n");
                    }
                    else
                    {
                        for (int i = 0; i < MESSAGE_COUNT; i++)
                        {
                            double avgWindSpeed = 10.0;
                            static char msgText[1024];
                            sprintf_s(msgText, sizeof(msgText), "{\"deviceId\":%s,\"windSpeed\":%.2f, \"i\":%d}", deviceId, avgWindSpeed + (rand() % 4 + 2), i);
                            IOTHUB_MESSAGE_HANDLE messageHandle = IoTHubMessage_CreateFromByteArray((const unsigned char*)msgText, strlen(msgText));
                            if (messageHandle == NULL)
                            {
                                (void)printf("IoTHubMessage_CreateFromByteArray failed\n");
                                break;
                            }
                            else
                            {
                                IOTHUB_MESSAGE_RESULT iotHubMessageResult;
                                const char* MSG_ID = "Sample_MessageId";
                                const char* MSG_CORRELATION_ID = "Sample_MessageCorrelationId";
                                const char* MSG_PROP_KEYS[3] = { "Sample_Key1", "Sample_Key2", "Sample_Key3" };
                                const char* MSG_PROP_VALS[3] = { "Sample_Val1", "Sample_Val2", "Sample_Val3" };

                                iotHubMessageResult = IoTHubMessage_SetMessageId(messageHandle, MSG_ID);
                                if (iotHubMessageResult != IOTHUB_MESSAGE_OK)
                                {
                                    (void)printf("IoTHubMessage_SetMessageId failed. Exiting...\n");
                                    IoTHubMessage_Destroy(messageHandle);
                                    break;
                                }
                                else
                                {
                                    iotHubMessageResult = IoTHubMessage_SetCorrelationId(messageHandle, MSG_CORRELATION_ID);
                                    if (iotHubMessageResult != IOTHUB_MESSAGE_OK)
                                    {
                                        (void)printf("IoTHubMessage_SetCorrelationId failed. Exiting...\n");
                                        IoTHubMessage_Destroy(messageHandle);
                                        break;
                                    }
                                    else
                                    {
                                        MAP_HANDLE mapHandle = IoTHubMessage_Properties(messageHandle);
                                        for (size_t j = 0; j < 3; j++)
                                        {
                                            if (Map_AddOrUpdate(mapHandle, MSG_PROP_KEYS[j], MSG_PROP_VALS[j]) != MAP_OK)
                                            {
                                                (void)printf("ERROR: Map_AddOrUpdate failed for property %zu!\r\n", j);
                                            }
                                        }

                                        iotHubMessagingResult = IoTHubMessaging_LL_Send(iotHubMessagingHandle, deviceId, messageHandle, sendCompleteCallback, NULL);
                                        if (iotHubMessagingResult != IOTHUB_MESSAGING_OK)
                                        {
                                            (void)printf("IoTHubMessaging_LL_Send failed\n");
                                        }
                                        else
                                        {
                                            (void)printf("IoTHubMessaging_LL_Send accepted data for transmission to IoT Hub.\r\n");
                                        }
                                    }
                                }
                            }
                            IoTHubMessage_Destroy(messageHandle);
                        }

                        feedbackCount = 0;
                        while (feedbackCount < MESSAGE_COUNT)
                        {
                            IoTHubMessaging_LL_DoWork(iotHubMessagingHandle);
                            ThreadAPI_Sleep(1);
                        }

                        /* Wait for user to press a key. */
                        (void)printf("Press any key to exit the application. \r\n");
                        (void)getchar();

                        IoTHubMessaging_LL_Close(iotHubMessagingHandle);
                    }
                }
                (void)printf("Calling IoTHubMessaging_LL_Destroy...\n");
                IoTHubMessaging_LL_Destroy(iotHubMessagingHandle);
            }
            (void)printf("Calling IoTHubServiceClientAuth_Destroy...\n");
            IoTHubServiceClientAuth_Destroy(iotHubServiceClientHandle);
        }
        platform_deinit();
    }
}