对于一个学校项目，我正在使用 IoT Hub 连接不同的设备 (ESP32)，目的是使用 Web 应用程序从设备检索数据。我想通过使用直接方法来做到这一点。
现在我在过去看到了一些使用 python 的直接方法，以及我如何在 Azure Functions 中使用它，但还没有在 ESP32 上使用它。顺便说一下，我在 ESP32 上用 C 编程。
有人有这方面的示例代码吗？我没有找到太多关于 C 中直接方法的信息，库是“azure-sdk-for-c-arduino”。
提前致谢
我目前的代码（这是测试代码）：
// Copyright (c) Microsoft Corporation. All rights reserved.
// SPDX-License-Identifier: MIT
/*
This is an Arduino-based Azure IoT Hub sample for ESPRESSIF ESP32 boards.
It uses our Azure Embedded SDK for C to help interact with Azure IoT.
For reference, please visit https://github.com/azure/azure-sdk-for-c.
To connect and work with Azure IoT Hub you need an MQTT client, connecting, subscribing
and publishing to specific topics to use the messaging features of the hub.
Our azure-sdk-for-c is an MQTT client support library, helping composing and parsing the
MQTT topic names and messages exchanged with the Azure IoT Hub.
This sample performs the following tasks:
- Synchronize the device clock with a NTP server;
- Initialize our "az_iot_hub_client" (struct for data, part of our azure-sdk-for-c);
- Initialize the MQTT client (here we use ESPRESSIF's esp_mqtt_client, which also handle the tcp connection and TLS);
- Connect the MQTT client (using server-certificate validation, SAS-tokens for client authentication);
- Periodically send telemetry data to the Azure IoT Hub.
To properly connect to your Azure IoT Hub, please fill the information in the `iot_configs.h` file.
*/
//Variabeles for drukknop
const int PushButton = 35;
//Variables for weight sensor;
double weight = 5.0;
// C99 libraries
#include <cstdlib>
#include <string.h>
#include <time.h>
// Libraries for MQTT client and WiFi connection
#include <WiFi.h>
#include <mqtt_client.h>
// Azure IoT SDK for C includes
#include <az_core.h>
#include <az_iot.h>
#include <azure_ca.h>
// Libraries for SendingJson
#include <ArduinoJson.h>
// Additional sample headers
#include "AzIoTSasToken.h"
#include "SerialLogger.h"
#include "iot_configs.h"
// When developing for your own Arduino-based platform,
// please follow the format '(ard;<platform>)'.
#define AZURE_SDK_CLIENT_USER_AGENT "c/" AZ_SDK_VERSION_STRING "(ard;esp32)"
// Utility macros and defines
#define sizeofarray(a) (sizeof(a) / sizeof(a[0]))
#define NTP_SERVERS "pool.ntp.org", "time.nist.gov"
#define MQTT_QOS1 1
#define DO_NOT_RETAIN_MSG 0
#define SAS_TOKEN_DURATION_IN_MINUTES 60
#define UNIX_TIME_NOV_13_2017 1510592825
#define PST_TIME_ZONE -8
#define PST_TIME_ZONE_DAYLIGHT_SAVINGS_DIFF 1
#define GMT_OFFSET_SECS (PST_TIME_ZONE * 3600)
#define GMT_OFFSET_SECS_DST ((PST_TIME_ZONE + PST_TIME_ZONE_DAYLIGHT_SAVINGS_DIFF) * 3600)
// Translate iot_configs.h defines into variables used by the sample
static const char* ssid = IOT_CONFIG_WIFI_SSID;
static const char* password = IOT_CONFIG_WIFI_PASSWORD;
static const char* host = IOT_CONFIG_IOTHUB_FQDN;
static const char* mqtt_broker_uri = "mqtts://" IOT_CONFIG_IOTHUB_FQDN;
static const char* device_id = IOT_CONFIG_DEVICE_ID;
static const int mqtt_port = AZ_IOT_DEFAULT_MQTT_CONNECT_PORT;
// Memory allocated for the sample's variables and structures.
static esp_mqtt_client_handle_t mqtt_client;
static az_iot_hub_client client;
static char mqtt_client_id[128];
static char mqtt_username[128];
static char mqtt_password[200];
static uint8_t sas_signature_buffer[256];
static unsigned long next_telemetry_send_time_ms = 0;
static char telemetry_topic[128];
static uint8_t telemetry_payload[100];
static uint32_t telemetry_send_count = 0;
#define INCOMING_DATA_BUFFER_SIZE 128
static char incoming_data[INCOMING_DATA_BUFFER_SIZE];
// Auxiliary functions
#ifndef IOT_CONFIG_USE_X509_CERT
static AzIoTSasToken sasToken(
&client,
AZ_SPAN_FROM_STR(IOT_CONFIG_DEVICE_KEY),
AZ_SPAN_FROM_BUFFER(sas_signature_buffer),
AZ_SPAN_FROM_BUFFER(mqtt_password));
#endif // IOT_CONFIG_USE_X509_CERT
static void connectToWiFi()
{
Logger.Info("Connecting to WIFI SSID " + String(ssid));
WiFi.mode(WIFI_STA);
WiFi.begin(ssid, password);
while (WiFi.status() != WL_CONNECTED)
{
delay(500);
Serial.print(".");
}
Serial.println("");
Logger.Info("WiFi connected, IP address: " + WiFi.localIP().toString());
}
static void initializeTime()
{
Logger.Info("Setting time using SNTP");
configTime(GMT_OFFSET_SECS, GMT_OFFSET_SECS_DST, NTP_SERVERS);
time_t now = time(NULL);
while (now < UNIX_TIME_NOV_13_2017)
{
delay(500);
Serial.print(".");
now = time(nullptr);
}
Serial.println("");
Logger.Info("Time initialized!");
}
void receivedCallback(char* topic, byte* payload, unsigned int length)
{
Logger.Info("Received [");
Logger.Info(topic);
Logger.Info("]: ");
for (int i = 0; i < length; i++)
{
Serial.print((char)payload[i]);
}
Serial.println("");
}
static esp_err_t mqtt_event_handler(esp_mqtt_event_handle_t event)
{
switch (event->event_id)
{
int i, r;
case MQTT_EVENT_ERROR:
Logger.Info("MQTT event MQTT_EVENT_ERROR");
break;
case MQTT_EVENT_CONNECTED:
Logger.Info("MQTT event MQTT_EVENT_CONNECTED");
r = esp_mqtt_client_subscribe(mqtt_client, AZ_IOT_HUB_CLIENT_C2D_SUBSCRIBE_TOPIC, 1);
if (r == -1)
{
Logger.Error("Could not subscribe for cloud-to-device messages.");
}
else
{
Logger.Info("Subscribed for cloud-to-device messages; message id:" + String(r));
}
break;
case MQTT_EVENT_DISCONNECTED:
Logger.Info("MQTT event MQTT_EVENT_DISCONNECTED");
break;
case MQTT_EVENT_SUBSCRIBED:
Logger.Info("MQTT event MQTT_EVENT_SUBSCRIBED");
break;
case MQTT_EVENT_UNSUBSCRIBED:
Logger.Info("MQTT event MQTT_EVENT_UNSUBSCRIBED");
break;
case MQTT_EVENT_PUBLISHED:
Logger.Info("MQTT event MQTT_EVENT_PUBLISHED");
break;
case MQTT_EVENT_DATA:
Logger.Info("MQTT event MQTT_EVENT_DATA");
for (i = 0; i < (INCOMING_DATA_BUFFER_SIZE - 1) && i < event->topic_len; i++)
{
incoming_data[i] = event->topic[i];
}
incoming_data[i] = '\0';
Logger.Info("Topic: " + String(incoming_data));
for (i = 0; i < (INCOMING_DATA_BUFFER_SIZE - 1) && i < event->data_len; i++)
{
incoming_data[i] = event->data[i];
}
incoming_data[i] = '\0';
if (String(incoming_data) == "GETWEIGHT")
{
Logger.Info("Send Data To The Cloud ");
sendTelemetry();
}
else
{
Logger.Info("Data: " + String(incoming_data));
}
break;
case MQTT_EVENT_BEFORE_CONNECT:
Logger.Info("MQTT event MQTT_EVENT_BEFORE_CONNECT");
break;
default:
Logger.Error("MQTT event UNKNOWN");
break;
}
return ESP_OK;
}
static void initializeIoTHubClient()
{
az_iot_hub_client_options options = az_iot_hub_client_options_default();
options.user_agent = AZ_SPAN_FROM_STR(AZURE_SDK_CLIENT_USER_AGENT);
if (az_result_failed(az_iot_hub_client_init(
&client,
az_span_create((uint8_t*)host, strlen(host)),
az_span_create((uint8_t*)device_id, strlen(device_id)),
&options)))
{
Logger.Error("Failed initializing Azure IoT Hub client");
return;
}
size_t client_id_length;
if (az_result_failed(az_iot_hub_client_get_client_id(
&client, mqtt_client_id, sizeof(mqtt_client_id) - 1, &client_id_length)))
{
Logger.Error("Failed getting client id");
return;
}
if (az_result_failed(az_iot_hub_client_get_user_name(
&client, mqtt_username, sizeofarray(mqtt_username), NULL)))
{
Logger.Error("Failed to get MQTT clientId, return code");
return;
}
Logger.Info("Client ID: " + String(mqtt_client_id));
Logger.Info("Username: " + String(mqtt_username));
}
static int initializeMqttClient()
{
#ifndef IOT_CONFIG_USE_X509_CERT
if (sasToken.Generate(SAS_TOKEN_DURATION_IN_MINUTES) != 0)
{
Logger.Error("Failed generating SAS token");
return 1;
}
#endif
esp_mqtt_client_config_t mqtt_config;
memset(&mqtt_config, 0, sizeof(mqtt_config));
mqtt_config.uri = mqtt_broker_uri;
mqtt_config.port = mqtt_port;
mqtt_config.client_id = mqtt_client_id;
mqtt_config.username = mqtt_username;
#ifdef IOT_CONFIG_USE_X509_CERT
Logger.Info("MQTT client using X509 Certificate authentication");
mqtt_config.client_cert_pem = IOT_CONFIG_DEVICE_CERT;
mqtt_config.client_key_pem = IOT_CONFIG_DEVICE_CERT_PRIVATE_KEY;
#else // Using SAS key
mqtt_config.password = (const char*)az_span_ptr(sasToken.Get());
#endif
mqtt_config.keepalive = 30;
mqtt_config.disable_clean_session = 0;
mqtt_config.disable_auto_reconnect = false;
mqtt_config.event_handle = mqtt_event_handler;
mqtt_config.user_context = NULL;
mqtt_config.cert_pem = (const char*)ca_pem;
mqtt_client = esp_mqtt_client_init(&mqtt_config);
if (mqtt_client == NULL)
{
Logger.Error("Failed creating mqtt client");
return 1;
}
esp_err_t start_result = esp_mqtt_client_start(mqtt_client);
if (start_result != ESP_OK)
{
Logger.Error("Could not start mqtt client; error code:" + start_result);
return 1;
}
else
{
Logger.Info("MQTT client started");
return 0;
}
}
/*
@brief Gets the number of seconds since UNIX epoch until now.
@return uint32_t Number of seconds.
*/
static uint32_t getEpochTimeInSecs()
{
return (uint32_t)time(NULL);
}
static void establishConnection()
{
connectToWiFi();
initializeTime();
initializeIoTHubClient();
(void)initializeMqttClient();
}
static void getTelemetryPayload(az_span payload, az_span* out_payload)
{
az_span original_payload = payload;
payload = az_span_copy(
payload, AZ_SPAN_FROM_STR("{ \"deviceId\": "));
payload = az_span_copy(payload, AZ_SPAN_FROM_STR( IOT_CONFIG_DEVICE_ID ));
payload = az_span_copy(payload, AZ_SPAN_FROM_STR( "," ));
payload = az_span_copy(payload, AZ_SPAN_FROM_STR( "\" weight\": "));
(void)az_span_u32toa(payload, weight , &payload);
payload = az_span_copy(payload, AZ_SPAN_FROM_STR(" }"));
payload = az_span_copy_u8(payload, '\0');
*out_payload = az_span_slice(original_payload, 0, az_span_size(original_payload) - az_span_size(payload) - 1);
}
static void sendTelemetry()
{
az_span telemetry = AZ_SPAN_FROM_BUFFER(telemetry_payload);
Logger.Info("Sending telemetry ...");
// The topic could be obtained just once during setup,
// however if properties are used the topic need to be generated again to reflect the
// current values of the properties.
if (az_result_failed(az_iot_hub_client_telemetry_get_publish_topic(
&client, NULL, telemetry_topic, sizeof(telemetry_topic), NULL)))
{
Logger.Error("Failed az_iot_hub_client_telemetry_get_publish_topic");
return;
}
getTelemetryPayload(telemetry, &telemetry);
if (esp_mqtt_client_publish(
mqtt_client,
telemetry_topic,
(const char*)az_span_ptr(telemetry),
az_span_size(telemetry),
MQTT_QOS1,
DO_NOT_RETAIN_MSG)
== 0)
{
Logger.Error("Failed publishing");
}
else
{
Logger.Info("Message published successfully");
}
}
// Arduino setup and loop main functions.
void setup()
{
establishConnection();
pinMode(PushButton, INPUT);
}
void loop()
{
if (WiFi.status() != WL_CONNECTED)
{
connectToWiFi();
}
#ifndef IOT_CONFIG_USE_X509_CERT
else if (sasToken.IsExpired())
{
Logger.Info("SAS token expired; reconnecting with a new one.");
(void)esp_mqtt_client_destroy(mqtt_client);
initializeMqttClient();
}
#endif
int Push_button_state = digitalRead(PushButton);
// if condition checks if push button is pressed
if ( Push_button_state == HIGH )
{
Serial.println("De Button Is ingedrukt");
sendTelemetry();
delay(500);
}
}
想法是，当我发送直接方法“GETWEIGHT”时，我会得到一个 json 值。
在您的
initializeMqttClient mqtt_client.setCallback(receivedCallback);
您的
receivedCallbackvoid receivedCallback(char* topic, byte* payload, unsigned int length)
{
Logger.Info("Received [");
Logger.Info(topic);
Logger.Info("]: ");
for (int i = 0; i < length; i++)
{
Serial.print((char)payload[i]);
}
Serial.println("");
}
你提到你想从设备中检索数据，所以你可能想回复消息。这是通过发送有关正确主题的消息来完成的。您需要包括状态（例如 200 表示“OK”）和直接方法的 ID。当您收到直接方法时，会包含此 ID。例如，如果您收到 ID 为 42 的直接方法，您可以通过发布来响应它：
void RespondToDirectMethod()
{
mqtt_client.publish("$iothub/methods/res/200/?$rid=42", "", false);
}
在你的
mqtt_event_handler你订阅了
AZ_IOT_HUB_CLIENT_C2D_SUBSCRIBE_TOPICAZ_IOT_HUB_CLIENT_METHODS_SUBSCRIBE_TOPIC