如何使用 Microsoft azure 客户端 sdk c 从物联网中心消息中获取 EventEnqueuedUtcTime

Question

我根据提供的示例创建了以下 C 程序，以便从物联网中心获取消息：

// Copyright (c) Microsoft. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for full license information.

#include <stdio.h>
#include <stdlib.h>
#include <iostream>
#include <fstream>
#include <string>
#include "azure_c_shared_utility/shared_util_options.h"
#include "iothub_client.h"
#include "iothub_message.h"
#include "azure_c_shared_utility/threadapi.h"
#include "azure_c_shared_utility/crt_abstractions.h"
#include "azure_c_shared_utility/platform.h"
#include "iothubtransportmqtt.h"
#include "iothub_client_options.h"
#include "iothub_device_client_ll.h"
#include "iothub_device_client.h"
#include "iothub_client_sample_mqtt_esp8266.h"

/*String containing Hostname, Device Id & Device Key in the format:                         */
/*  "HostName=<host_name>;DeviceId=<device_id>;SharedAccessKey=<device_key>"                */
/*  "HostName=<host_name>;DeviceId=<device_id>;SharedAccessSignature=<device_sas_token>"    */
static const char* connectionString = "HostName=mydevice";

static int callbackCounter;
//static char msgText[1024];
//static char propText[1024];
static bool g_continueRunning;
#define MESSAGE_COUNT 50
#define SET_TRUSTED_CERT_IN_SAMPLES
#define DOWORK_LOOP_NUM     3

#ifdef SET_TRUSTED_CERT_IN_SAMPLES
#include "certs.h"
#endif 

typedef struct EVENT_INSTANCE_TAG
{
    IOTHUB_MESSAGE_HANDLE messageHandle;
    size_t messageTrackingId;  // For tracking the messages within the user callback.
} EVENT_INSTANCE;

static IOTHUBMESSAGE_DISPOSITION_RESULT ReceiveMessageCallback(IOTHUB_MESSAGE_HANDLE message, void* userContextCallback)
{
    int* counter = (int*)userContextCallback;
    const char* buffer;
    size_t size;
    MAP_HANDLE mapProperties;
    const char* messageId;
    const char* correlationId;

    // Message properties
    if ((messageId = IoTHubMessage_GetMessageId(message)) == NULL)
    {
        messageId = "<null>";
    }

    if ((correlationId = IoTHubMessage_GetCorrelationId(message)) == NULL)
    {
        correlationId = "<null>";
    }

    // Message content
    if (IoTHubMessage_GetByteArray(message, (const unsigned char**)&buffer, &size) != IOTHUB_MESSAGE_OK)
    {
        (void)printf("unable to retrieve the message data\r\n");
    }
    else
    {
        (void)printf("Received Message [%d]\r\n Message ID: %s\r\n Correlation ID: %s\r\n Data: <<<%.*s>>> & Size=%d\r\n", *counter, messageId, correlationId, (int)size, buffer, (int)size);
        // If we receive the work 'quit' then we stop running
        if (size == (strlen("quit") * sizeof(char)) && memcmp(buffer, "quit", size) == 0)
        {
            g_continueRunning = false;
        }
    }

    // Retrieve properties from the message
    mapProperties = IoTHubMessage_Properties(message);
    if (mapProperties != NULL)
    {
        const char*const* keys;
        const char*const* values;
        size_t propertyCount = 0;
        if (Map_GetInternals(mapProperties, &keys, &values, &propertyCount) == MAP_OK)
        {
            if (propertyCount > 0)
            {
                size_t index;
                std::string uid;
                printf(" Message Properties:\r\n");
                for (index = 0; index < propertyCount; index++)
                {
                    (void)printf("\tKey: %s Value: %s\r\n", keys[index], values[index]);
                    if (std::strcmp(keys[index],"uid") == 0 )
                    {
                        uid =  values[index];
                        std::cout << "uid is " << uid << std::endl;
                    }

                }
                (void)printf("\r\n");
            }
        }
    }

    /* Some device specific action code goes here... */
    (*counter)++;
    return IOTHUBMESSAGE_ACCEPTED;
}

// static void SendConfirmationCallback(IOTHUB_CLIENT_CONFIRMATION_RESULT result, void* userContextCallback)
// {
//     EVENT_INSTANCE* eventInstance = (EVENT_INSTANCE*)userContextCallback;
//     size_t id = eventInstance->messageTrackingId;

//     (void)printf("Confirmation[%d] received for message tracking id = %d with result = %s\r\n", callbackCounter, (int)id, MU_ENUM_TO_STRING(IOTHUB_CLIENT_CONFIRMATION_RESULT, result));
//     /* Some device specific action code goes here... */
//     callbackCounter++;
//     IoTHubMessage_Destroy(eventInstance->messageHandle);
// }

static void connection_status_callback(IOTHUB_CLIENT_CONNECTION_STATUS result, IOTHUB_CLIENT_CONNECTION_STATUS_REASON reason, void* user_context)
{
    (void)reason;
    (void)user_context;
    // This sample DOES NOT take into consideration network outages.
    if (result == IOTHUB_CLIENT_CONNECTION_AUTHENTICATED)
    {
        (void)printf("The device client is connected to iothub\r\n");
    }
    else
    {
        (void)printf("The device client has been disconnected\r\n");
    }
}

void iothub_client_sample_mqtt_esp8266_run(void)
{

    IOTHUB_CLIENT_HANDLE iotHubClientHandle;
    g_continueRunning = true;
    srand((unsigned int)time(NULL));

    callbackCounter = 0;
    int receiveContext = 0;

    if (platform_init() != 0)
    {
        (void)printf("Failed to initialize the platform.\r\n");
    }
    else
    {
        if ((iotHubClientHandle = IoTHubClient_CreateFromConnectionString(connectionString, MQTT_Protocol)) == NULL)
        {
            (void)printf("ERROR: iotHubClientHandle is NULL!\r\n");
        }
        else
        {
            bool traceOn = true;
            IoTHubClient_SetOption(iotHubClientHandle, OPTION_LOG_TRACE, &traceOn);
            #ifdef SET_TRUSTED_CERT_IN_SAMPLES
            // For mbed add the certificate information
                  if (IoTHubClient_SetOption(iotHubClientHandle, "TrustedCerts", certificates) != IOTHUB_CLIENT_OK)
                   {
                       (void)printf("failure to set option \"TrustedCerts\"\r\n");
                   }
            #endif
            (void)IoTHubDeviceClient_SetConnectionStatusCallback(iotHubClientHandle, connection_status_callback, NULL);
            /* Setting Message call back, so we can receive Commands. */
            if (IoTHubClient_SetMessageCallback(iotHubClientHandle, ReceiveMessageCallback, &receiveContext) != IOTHUB_CLIENT_OK)
            {
                (void)printf("ERROR: IoTHubClient_LL_SetMessageCallback..........FAILED!\r\n");
            }
            else
            {
                (void)printf("IoTHubClient_LL_SetMessageCallback...successful.\r\n");

                while (g_continueRunning)
                {
                  ThreadAPI_Sleep(1000);
                }

            }
            IoTHubClient_Destroy(iotHubClientHandle);
        }
        platform_deinit();
    }
}

int main(void)
{
    iothub_client_sample_mqtt_esp8266_run();
    return 0;
}

一切正常。我正确地获得了 messageid 和 correlationid。但是我想在我的回调中收到 EventEnqueuedUtcTime，这里提到了 https://docs.microsoft.com/en-us/azure/stream-analytics/stream-analytics-define-inputs#configure-an-iot-hub-as-a-data-stream-input.

由于我对这个 SDK 还很陌生，所以我没有办法实现它。有人有想法吗？

Answer 1

我认为您混淆了设备 SDK 和服务 SDK。 EventEnqueuedUtcTime 可用于读取设备发送到 IoT 中心的遥测数据的服务端应用程序。我假设您希望通过云到设备消息传递到您的设备的消息获得相同的值，该消息将传递到您的回调函数 ReceiveMessageCallback。属性不会添加到从云到设备的消息中，只有从设备到云的消息。

如何使用 Microsoft azure 客户端 sdk c 从物联网中心消息中获取 EventEnqueuedUtcTime

How to get EventEnqueuedUtcTime from iot hub message using microsoft azure client sdk c

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