The following code doesn't compile when adding the first include (#include <QtWebSockets/QtWebSockets>).
error C1083: Cannot open include file: 'QObject': No such file or directory... this happens in qmaskgenerator.h
I really think in qmaskgenerator.h, QtCore is missing in front of QObject (it should be #include<QtCore/QObject>). This solve the problem for me...

#include <QtWebSockets/QtWebSockets>
#include <QtCore/QCoreApplication>
#include <iostream>

int main(int argc, char *argv[])

{ QCoreApplication app(argc, argv); std::cout<<"hello world!" << std::endl; return app.exec(); }