HTTPClientSession::proxyConnect() function tries to resolve the name of the target host by doing:
SocketAddress targetAddress(getHost(), getPort());
HTTPRequest proxyRequest(HTTPRequest::HTTP_CONNECT, targetAddress.toString(), HTTPMessage::HTTP_1_1);
This is not necessary, and in some environment, where DNS doesn't work, this will fail. When HTTP proxy is used, normally don't have to do DNS. Just put the host name into the proxyRequest is all required. So a fix like this would be better:
std::string dest = getHost();
dest.append(":");
NumberFormatter::append(dest, getPort());
HTTPRequest proxyRequest(HTTPRequest::HTTP_CONNECT, dest, HTTPMessage::HTTP_1_1);
