c http json

您需要对应用程序使用HTTP通信并使用JSON格式进行数据交换。下面是一个使用C语言进行HTTP请求并解析JSON响应的示例代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <curl/curl.h>
#include <jansson.h>

int main(void)
{
    CURL *curl;
    CURLcode res;
    char *url = "http://example.com/api";
    char *post_data = "{\"key\": \"value\"}";

    curl = curl_easy_init();
    if (curl) {
        struct curl_slist *headers = NULL;
        headers = curl_slist_append(headers, "Content-Type: application/json");

        curl_easy_setopt(curl, CURLOPT_URL, url);
        curl_easy_setopt(curl, CURLOPT_POSTFIELDS, post_data);
        curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);

        res = curl_easy_perform(curl);
        if (res != CURLE_OK) {
            fprintf(stderr, "curl_easy_perform() failed: %s\n", curl_easy_strerror(res));
        } else {
            long http_code = 0;
            curl_easy_getinfo(curl, CURLINFO_RESPONSE_CODE, &http_code);
            printf("HTTP Status Code: %ld\n", http_code);

            json_error_t error;
            json_t *root = json_loads(post_data, 0, &error);
            if (!root) {
                fprintf(stderr, "json_loads() failed: %s\n", error.text);
            } else {
                json_t *result = NULL;
                json_object_get(root, "result", &result);
                if (result) {
                    const char *result_str = json_string_value(result);
                    printf("Result: %s\n", result_str);
                } else {
                    fprintf(stderr, "Failed to get 'result' field from JSON response.\n");
                }

                json_decref(root);
            }
        }

        curl_slist_free_all(headers);
        curl_easy_cleanup(curl);
    }

    return 0;
}

这个示例使用了`curl`库来进行HTTP请求，使用`jansson`库来解析JSON响应。您需要安装这两个库才能编译和运行示例代码。