在一些物聯網應用場景中，我們需要從服務器或者其它設備中獲取來自網絡的JSON包來實現數據的傳輸和控制。下面是一些ESP32獲取JSON包的常見方式。

使用Arduino IDE

#include <WiFi.h>
#include <HTTPClient.h>
void setup() {
Serial.begin(115200);
WiFi.begin("your_SSID", "your_PASSWORD");
while (WiFi.status() != WL_CONNECTED) {
delay(1000);
Serial.println("Connecting to WiFi..");
} 
String url = "http://your_api_url";  // 注意URL需要http或https前綴
HTTPClient http;
http.begin(url);
int httpCode = http.GET();
if (httpCode >0) {
String payload = http.getString();
Serial.println(payload);
}
http.end();
}
void loop() {
}

使用ESP-IDF

#include "esp_http_client.h"
void http_event_handler(esp_http_client_event_t *evt)
{
switch(evt->event_id) {
case HTTP_EVENT_ON_DATA:
ESP_LOGI(TAG, "HTTP_EVENT_ON_DATA, len=%d", evt->data_len);
if (!esp_http_client_is_chunked_response(evt->client)) {
printf("%.*s", evt->data_len, (char*)evt->data);
}
case HTTP_EVENT_ON_FINISH:
ESP_LOGI(TAG, "HTTP_EVENT_ON_FINISH");
break;
case HTTP_EVENT_DISCONNECTED:
ESP_LOGI(TAG, "HTTP_EVENT_DISCONNECTED");
break;
}
}
esp_http_client_config_t config = {
.url = "http://your_api_url",
.event_handler = http_event_handler,
};
esp_http_client_handle_t client = esp_http_client_init(&config);
esp_err_t err = esp_http_client_perform(client);
if (err == ESP_OK) {
ESP_LOGI(TAG, "HTTP GET Status = %d, content_length = %d",
esp_http_client_get_status_code(client),
esp_http_client_get_content_length(client));
} else {
ESP_LOGE(TAG, "HTTP GET request failed: %s", esp_err_to_name(err));
}

無論你選擇什么方式獲取JSON數據，都需要了解JSON格式并且解析你獲取到的數據以便后續的數據處理工作。