NOTE! If this page is served from https, you must use a wss:// url. To connect to a
websocket through HTTP, save this page and its scripts and run locally.
The stress test starts 100 sockets. They will each append 10 numbers to a document,
one number at a time. By the end of the test, the document should consisting of the numbers 0,1,2,...,999
as a long text string. Only one client can modify the document at a time, so for each successful append,
all of the other clients will fail and need to re-append the next number.