To see the library in action, you can take a look at a project that I made: lazerdrive-leaderboard-sniffer
You must have a Qt5 sdk installed (packages qt5-qmake qt5-default) with websockets support (libqt5websockets5-dev). To build it, you need the build-essential package.
qmake
make
make install
You can also use Qt Creator if you are not familiar with a shell.