我基于提供的示例创建了以下c程序，只是为了从iot hub获得消息：
// 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，在这里提到https://docs.microsoft.com/en-us/azure/stream-analytics/stream-analytics-define-inputs#configure-an-iot-hub-as-a-data-stream-input。
由于我在这个SDK上还很陌生，所以没有办法实现这一目标。有人有主意吗？
您可以使用IoTHubMessage_GetProperty（）返回EventEnqueuedUtcTime属性吗？