Curl with wxThreads blocks thread after a few iterations - c++

Question

I'm writting a GUI application, that needs to periodically ask for data using requests, and then plot it in a widget. I created a wxThread which in Entry() ask for data using libcurl, then it shoots event to the main thread that activates plot updating function. But there is a strange issue with sending requests, always after a few iterations my request sending thread hangs, and when I kill it, then I got information about the error(Cannot connect to server.) Is there any way to make thread not to hang, but just ignore the error, and try to send request again? (This error only occours when server is online, when its offline I can get the error without hanging the thread.)
I thought it was due to some server error so I setted CURLOPT_TIMEOUT and CURLOPT_CONNECTIONTIMEOUT, but with no effect, just the name of the error changes after killing a thread to "Timeout error". Strangly enough when the colelcting data thread is restarted from GUI without closing the app it works perfectly. So It hangs only on the first run(exactly after 18-24 iterations) or I did not have opportunity to see it hangs again, but I did multiple tests.
Here is my code for sending, the app frezzes at curle_easy_perform(), it did not go into writting function.
struct stats
{
int y_data1;
int y_data2;
int x_data;
};
class OutputThread : public wxThread
{
public:
OutputThread(wxWindow* parent, std::string url) : wxThread(wxTHREAD_DETACHED)
{
_parentHandler = parent;
_url = url;
}
protected:
wxThread::ExitCode Entry()
{
while(!TestDestroy())
{
repidjson::Document response;
std::string raw_response = send_request(_url );
if(raw_response != "")
{
if(response.Parse(raw_response.c_str()).HasParseError())
{
std::cout << "Parse error!\n";
sleep(1);
continue;
}
else
{
stats new_stats;
new_stats.y_data1 = response["y_data1"].GetInt();
new_stats.y_data2 = response["y_data2"].GetInt();
new_stats.x_data = response["x_data"].GetInt();
wxCommandEvent event(wxEVT_COMMAND_OUTPUT_THREAD_UPDATE, wxID_ANY);
event.SetClientData(static_cast<void*>(&new_stats));
_parentHandler->GetEventHandler()->AddPendingEvent(event);
sleep(1);
}
}
}
}
private:
wxWindow* _parentHandler;
std::string _url;
};
std::string send_request(std::string url)
{
curl_global_init(CURL_GLOBAL_ALL);
auto handle = curl_easy_init();
std::stringstream returnData;
if(handle)
{
curl_easy_setopt(handle, CURLOPT_NOPROXY, "localhost");
curl_easy_setopt(handle, CURLOPT_URL, url.c_str());
curl_easy_setopt(handle, CURLOPT_WRITEFUNCTION, write_data);
curl_easy_setopt(handle, CURLOPT_WRITEDATA, &returnData);
curl_easy_setopt(handle, CURLOPT_TIMEOUT, 1L);
curl_easy_setopt(handle, CURLOPT_CONNECTTIMEOUT, 1L):
curl_easy_setopt(handle, CURLOPT_HTTPGET, 1);
auto ret = curl_easy_perform(handle); //here the thread hangs
if(ret != CURLE_OK)
{
std::cout << "curl_easy_perform() failed: " << curl_Easy_strerror(ret) << "\n";
returnData.clear();
returnData << "";
}
curl_easy_cleanup(handle);
}
curl_global_cleanup();
return returnData.str();
}
//Data writing function
size_t write_data(void* ptr, size_t size, size_t nmeb, void* stream)
{
std::string buf = std::string(static_cast<char*>(ptr), size * nmeb);
std::stringstream* response = static_cast<std::stringstream*>(stream);
response->write(buf.c_str(), (std::streamsize)buf.size());
return size*nmeb;
}
Parent is an wxPanel with graph and function that updates the plot.
wxEVT_COMMAND_OUTPUT_THREAD_UPDATE it is my custom event that activates plot updating function. I'm not sure if there is any point in reproducing the whole widget with graph so to make things short there is a button to start capturing data and to stop, what is equivalent of creating OutputThread and executing Entry() function until user press stop button.
Could it be a threading issue or is it just an error in sending function?