使用ESP-IDF写一段程序，启用web服务

好的，我会尽力回答您的问题。

下面是使用 ESP-IDF 开启 web 服务的示例程序：

#include <esp_wifi.h>
#include <esp_event.h>
#include <esp_log.h>
#include <esp_system.h>
#include <nvs_flash.h>
#include <sys/param.h>
#include "nvs_flash.h"
#include "tcpip_adapter.h"
#include "esp_eth.h"

#include "esp_http_server.h"

static const char *TAG = "example";

/* An HTTP GET handler */
esp_err_t hello_get_handler(httpd_req_t *req)
{
    char*  buf;
    size_t buf_len;

    /* Get header value string length and allocate memory for length + 1,
     * extra byte for null termination */
    buf_len = httpd_req_get_hdr_value_len(req, "Host") + 1;
    if (buf_len > 1) {
        buf = malloc(buf_len);
        /* Copy null terminated value string into buffer */
        if (httpd_req_get_hdr_value_str(req, "Host", buf, buf_len) == ESP_OK) {
            ESP_LOGI(TAG, "Found header => Host: %s", buf);
        }
        free(buf);
    }

    buf_len = httpd_req_get_hdr_value_len(req, "Test-Header-2") + 1;
    if (buf_len > 1) {
        buf = malloc(buf_len);
        if (httpd_req_get_hdr_value_str(req, "Test-Header-2", buf, buf_len) == ESP_OK) {
            ESP_LOGI(TAG, "Found header => Test-Header-2: %s", buf);
        }
        free(buf);
    }

    buf_len = httpd_req_get_hdr_value_len(req, "Test-Header-1") + 1;
    if (buf_len > 1) {
        buf = malloc(buf_len);
        if (httpd_req_get_hdr_value_str(req, "Test-Header-1", buf, buf_len) == ESP_OK) {
            ESP_LOGI(TAG, "Found header => Test-Header-1: %s", buf);
        }
        free(buf);
    }

    /* Read URL query string length and allocate memory for length + 1,
     * extra byte for null termination */
    buf_len = httpd_req_get_url_query_len(req) + 1;
    if (buf_len > 1) {
        buf = malloc(buf_len);
        if (httpd_req_get_url_query_str(req, buf, buf_len) == ESP_OK) {
            ESP_LOGI(TAG, "Found URL query =>