Use the mouse to draw on the canvas below -- all other browser windows open
on this page see your drawing in realtime and you can see any of theirs as
The lws-mirror protocol doesn't interpret what is being sent to it, it just
re-sends it to every other websocket it has a connection with using that
protocol, including the guy who sent the packet.
libwebsockets-test-client joins in by spamming circles on to this
shared canvas when run.