CURL *curl;

	CURLcode res;

	struct curl_slist *headers=NULL; // init to NULL is important

    headers = curl_slist_append(headers, "Accept: application/json");  

	curl = curl_easy_init();

	if(curl) {

		curl_easy_setopt(curl, CURLOPT_URL, "http://web.com/api/json/123");//cant get json file

		curl_easy_setopt(curl, CURLOPT_URL, "http://web.com/pages/123.html");//this returns entire webpage

		curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);

		curl_easy_setopt(curl, CURLOPT_RETURNTRANSFER, true);

	    res = curl_easy_perform(curl);

		if(CURLE_OK == res) {

			char *ct;

			// ask for the content-type

		    res = curl_easy_getinfo(curl, CURLINFO_CONTENT_TYPE, &ct);

			if((CURLE_OK == res) && ct)

		        printf("We received Content-Type: %s\n", ct);

		}

	}

    // always cleanup

    curl_easy_cleanup(curl);

//参考答案1

std::string ServerContent::DownloadJSO

N(std::string URL)
{
      
      CURL *curl;
      CURLcode res;
      struct curl_slist *headers=NULL; // init to NULL is important
      std::ostringstream oss;
       curl_slist_append(headers, "Accept: application/json");  
      curl_slist_append( headers, "Content-Type: application/json");
      curl_slist_append( headers, "charsets: utf-8");
       curl = curl_easy_init();

if(curl) {
            curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
            curl_easy_setopt(curl, CURLOPT_URL, URL.c_str());
            curl_easy_setopt(curl, CURLOPT_HTTPGET,1);
            curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
            curl_easy_setopt(curl,CURLOPT_WRITEFUNCTION,writer);
            res = curl_easy_perform(curl);
            if(CURLE_OK == res) {
                  char *ct;        
                  res = curl_easy_getinfo(curl, CURLINFO_CONTENT_TYPE, &ct);
                  if((CURLE_OK == res) && ct)
                        return *DownloadedResponse;
            }
      }

}