问为什么libcurl有时会抱怨“无法解析主机名”？

EN

size_t Http::WriteMemoryCallback(void *contents, size_t size, size_t nmemb, void *userp)
{
    size_t realsize = size * nmemb;
    MemoryStruct *mem = (MemoryStruct *)userp;

    mem->memory = (char *)realloc(mem->memory, mem->size + realsize + 1);
    assert(NULL != mem->memory);
    memcpy(&(mem->memory[mem->size]), contents, realsize);
    mem->size += realsize;
    mem->memory[mem->size] = 0;

    return realsize;
}

void Http::run(const URL &url, Http::FinishedCallback cbk)
{
    CURL *handle = curl_easy_init();
    if (handle) 
    {

        MemoryStruct *chunk = new MemoryStruct;
        chunk->memory = (char *)malloc(1);  /* will be grown as needed by the realloc above */
        chunk->size = 0;    /* no data at this point */


        CURLcode res; 
        curl_easy_setopt(handle, CURLOPT_URL, url.getUrl().c_str());
        curl_easy_setopt(handle, CURLOPT_WRITEDATA, (void *)chunk);
        curl_easy_setopt(handle, CURLOPT_WRITEFUNCTION, WriteMemoryCallback);
        curl_easy_setopt(handle, CURLOPT_USERAGENT, "libcurl-agent/1.0");
        curl_easy_setopt(handle, CURLOPT_TIMEOUT, 10L);
        curl_easy_setopt(handle, CURLOPT_CONNECTTIMEOUT, 10L);
        res = curl_easy_perform(handle);

        /* check for errors */
        if (CURLE_OK != res) 
        {
            chunk->status = false;
            std::string errCode = std::to_string(res);
            chunk->memory = (char *)realloc(chunk->memory, chunk->size + errCode.size() + 1);
            memcpy(&(chunk->memory[chunk->size]), errCode.c_str(), errCode.size());
            chunk->size += errCode.size();
            chunk->memory[chunk->size] = 0;
        }
        else 
        {
            chunk->status = true;
        }

#ifdef _DEBUG
        chunk->url = url;
#endif
        cbk(chunk);
        free(chunk);
        curl_easy_cleanup(handle);
    }
}


void Http::get(URL url, FinishedCallback cbk)
{
    std::thread http(&Http::run, Http(), url, cbk);
    http.detach();
}

Http::~Http()
{
    curl_global_cleanup();
}

int index = 0;
bool finish = false;
void func(Http::MemoryStruct *memo)
{
    if (!memo->status)
    {
#ifdef _DEBUG
        LOG(INFO) << "Failure:\t" << curl_easy_strerror((CURLcode)atoi(memo->memory)) << "\n";

#endif
    }
    else
    {
        //LOG(INFO) << memo->memory << '\n';
    }
    finish = memo->status;
    ++index;
}

int main(void)
{
    curl_global_init(CURL_GLOBAL_ALL);
    URL::AttribMap attribMap{ { "class", "System" }, { "token", "KY0SQ3FX996PU1ZO" }, { "type", "GetConfig" } };
    URL url("open.55.la", "/index.php", attribMap);
    Http http;
    while(index++ <=10)
    {
            try
            {
                http.get(url, func);
            }
            catch (std::_System_error &err)
            {
                LOG(INFO) << err.what();
            }
    }
    while (true)
    {
        ;
    }
    el::Loggers::flushAll();
    return EXIT_SUCCESS;
}