int main(void)
{
    IOTHUB_CLIENT_TRANSPORT_PROVIDER protocol;
    IOTHUB_MESSAGE_HANDLE message_handle;
    size_t messages_sent = 0;
    const char* telemetry_msg = "test_message";

    // 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

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

    IOTHUB_DEVICE_CLIENT_LL_HANDLE device_ll_handle;

    (void)printf("Creating IoTHub Device handle\r\n");
    // Create the iothub handle here
    device_ll_handle = IoTHubDeviceClient_LL_CreateFromConnectionString(connectionString, protocol);
    if (device_ll_handle == NULL)
    {
        (void)printf("Failure createing Iothub device.  Hint: Check you connection string.\r\n");
    }
    else
    {
        // Set any option that are neccessary.
        // For available options please see the iothub_sdk_options.md documentation

        bool traceOn = true;
        IoTHubDeviceClient_LL_SetOption(device_ll_handle, OPTION_LOG_TRACE, &traceOn);

#ifdef SET_TRUSTED_CERT_IN_SAMPLES
        // Setting the Trusted Certificate.  This is only necessary on system with without
        // built in certificate stores.
            IoTHubDeviceClient_LL_SetOption(device_ll_handle, OPTION_TRUSTED_CERT, certificates);
#endif // SET_TRUSTED_CERT_IN_SAMPLES

#if defined SAMPLE_MQTT || defined SAMPLE_MQTT_WS
        //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;
        //IoTHubDeviceClient_LL_SetOption(iothub_ll_handle, OPTION_AUTO_URL_ENCODE_DECODE, &urlEncodeOn);
#endif

        // Setting connection status callback to get indication of connection to iothub
        (void)IoTHubDeviceClient_LL_SetConnectionStatusCallback(device_ll_handle, connection_status_callback, NULL);

        do
        {
            if (messages_sent < MESSAGE_COUNT)
            {
                // Construct the iothub message from a string or a byte array
                message_handle = IoTHubMessage_CreateFromString(telemetry_msg);
                //message_handle = IoTHubMessage_CreateFromByteArray((const unsigned char*)msgText, strlen(msgText)));

                // 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 IoTHub\r\n", (int)(messages_sent + 1));
                IoTHubDeviceClient_LL_SendEventAsync(device_ll_handle, message_handle, send_confirm_callback, NULL);

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

                messages_sent++;
            }
            else if (g_message_count_send_confirmations >= MESSAGE_COUNT)
            {
                // After all messages are all received stop running
                g_continueRunning = false;
            }

            IoTHubDeviceClient_LL_DoWork(device_ll_handle);
            ThreadAPI_Sleep(1);

        } while (g_continueRunning);

        // Clean up the iothub sdk handle
        IoTHubDeviceClient_LL_Destroy(device_ll_handle);
    }
    // Free all the sdk subsystem
    IoTHub_Deinit();

    printf("Press any key to continue");
    getchar();

    return 0;
}
int main(void)
{
    TRANSPORT_HANDLE transport_handle;
    IOTHUB_CLIENT_TRANSPORT_PROVIDER protocol;
    IOTHUB_DEVICE_CLIENT_LL_HANDLE device_ll_handle1;
    IOTHUB_DEVICE_CLIENT_LL_HANDLE device_ll_handle2;

#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

    g_continueRunning = true;

    //callbackCounter = 0;
    int receiveContext1 = 0;
    int receiveContext2 = 0;

    (void)printf("Starting the IoTHub client shared sample.  Send `quit` message to either device to close...\r\n");

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

    if ((transport_handle = IoTHubTransport_Create(protocol, hubName, hubSuffix)) == NULL)
    {
        printf("Failed to creating the protocol handle.\r\n");
    }
    else
    {
        EVENT_INSTANCE device1_event;
        EVENT_INSTANCE device2_event;

        device1_event.deviceId = deviceId1;

        IOTHUB_CLIENT_DEVICE_CONFIG config1 = { 0 };
        config1.deviceId = deviceId1;
        config1.deviceKey = deviceKey1;
        config1.deviceSasToken = NULL;
        config1.protocol = protocol;
        config1.transportHandle = IoTHubTransport_GetLLTransport(transport_handle);

        device2_event.deviceId = deviceId2;

        IOTHUB_CLIENT_DEVICE_CONFIG config2 = { 0 };
        config2.deviceId = deviceId2;
        config2.deviceKey = deviceKey2;
        config2.deviceSasToken = NULL;
        config2.protocol = protocol;
        config2.transportHandle = IoTHubTransport_GetLLTransport(transport_handle);

        if ((device_ll_handle1 = IoTHubDeviceClient_LL_CreateWithTransport(&config1)) == NULL)
        {
            (void)printf("ERROR: iotHubClientHandle1 is NULL!\r\n");
        }
        else if ((device_ll_handle2 = IoTHubDeviceClient_LL_CreateWithTransport(&config2)) == NULL)
        {
            (void)printf("ERROR: iotHubClientHandle1 is NULL!\r\n");
        }
        else
        {
            // Set any option that are neccessary.
            // For available options please see the iothub_sdk_options.md documentation
            //bool traceOn = true;
            //IoTHubDeviceClient_LL_SetOption(device_ll_handle1, OPTION_LOG_TRACE, &traceOn);
            //IoTHubDeviceClient_LL_SetOption(device_ll_handle2, OPTION_LOG_TRACE, &traceOn);
#ifdef SET_TRUSTED_CERT_IN_SAMPLES
            // Setting the Trusted Certificate.  This is only necessary on system without
            // built in certificate stores.
            IoTHubDeviceClient_LL_SetOption(device_ll_handle1, OPTION_TRUSTED_CERT, certificates);
            IoTHubDeviceClient_LL_SetOption(device_ll_handle2, OPTION_TRUSTED_CERT, certificates);
#endif // SET_TRUSTED_CERT_IN_SAMPLES

#ifdef SAMPLE_HTTP
            unsigned int timeout = 241000;
            // Because it can poll "after 9 seconds" polls will happen effectively // at ~10 seconds.
            // Note that for scalabilty, the default value of minimumPollingTime
            // is 25 minutes. For more information, see:
            // https://azure.microsoft.com/documentation/articles/iot-hub-devguide/#messaging
            unsigned int minimumPollingTime = 9;
            IoTHubDeviceClient_LL_SetOption(device_ll_handle1, OPTION_MIN_POLLING_TIME, &minimumPollingTime);
            IoTHubDeviceClient_LL_SetOption(device_ll_handle1, OPTION_HTTP_TIMEOUT, &timeout);
            IoTHubDeviceClient_LL_SetOption(device_ll_handle2, OPTION_MIN_POLLING_TIME, &minimumPollingTime);
            IoTHubDeviceClient_LL_SetOption(device_ll_handle2, OPTION_HTTP_TIMEOUT, &timeout);
#endif // SAMPLE_HTTP

            /* Setting Message call back, so we can receive Commands. */
            (void)IoTHubDeviceClient_LL_SetMessageCallback(device_ll_handle1, ReceiveMessageCallback, &receiveContext1);
            (void)IoTHubDeviceClient_LL_SetMessageCallback(device_ll_handle2, ReceiveMessageCallback, &receiveContext2);

            /* Now that we are ready to receive commands, let's send some messages */
            size_t messages_sent = 0;
            IOTHUB_MESSAGE_HANDLE message_handle;
            do
            {
                if (messages_sent < MESSAGE_COUNT)
                {
                    // Create the event hub message
                    message_handle = create_events(&device1_event);
                    (void)IoTHubDeviceClient_LL_SendEventAsync(device_ll_handle1, message_handle, SendConfirmationCallback, &device1_event);
                    // The message is copied to the sdk so the we can destroy it
                    IoTHubMessage_Destroy(message_handle);

                    message_handle = create_events(&device2_event);
                    (void)IoTHubDeviceClient_LL_SendEventAsync(device_ll_handle2, message_handle, SendConfirmationCallback, &device2_event);
                    // The message is copied to the sdk so the we can destroy it
                    IoTHubMessage_Destroy(message_handle);

                    messages_sent++;
                }

                IoTHubDeviceClient_LL_DoWork(device_ll_handle1);
                IoTHubDeviceClient_LL_DoWork(device_ll_handle2);
                ThreadAPI_Sleep(1);
            } while (g_continueRunning);

            (void)printf("client_amqp_shared_sample has gotten quit message, call DoWork %d more time to complete final sending...\r\n", DOWORK_LOOP_NUM);
            for (size_t index = 0; index < DOWORK_LOOP_NUM; index++)
            {
                IoTHubDeviceClient_LL_DoWork(device_ll_handle1);
                IoTHubDeviceClient_LL_DoWork(device_ll_handle2);
                ThreadAPI_Sleep(1);
            }

            // Clean up the iothub sdk handle
            IoTHubDeviceClient_LL_Destroy(device_ll_handle1);
            IoTHubDeviceClient_LL_Destroy(device_ll_handle2);
        }
        IoTHubTransport_Destroy(transport_handle);
        // Free all the sdk subsystem
        IoTHub_Deinit();
    }
    return 0;
}