http.cc
line 447:
if (select(maxfd + 1, &fdread, &fdwrite, &fdexcep, nullptr) < 0)

"nullptr " Should use timeout:

struct timeval timeout;
timeout.tv_sec = xxx;
timeout.tv_usec = xxx;
select(maxfd+1, &fdread, &fdwrite, &fdexcep, &timeout);

and, You should add connection timeout and request timeout:
request.setOpt(new curlpp::Options::ConnectTimeout(2000));
request.setOpt(new curlpp::Options::Timeout(5));

The code is too rough.