Provide some way of checking for support

[Xandaros]

Not all browsers support websockets - it would be great to know if websockets are actually supported in the browser used, so you can fall back on something else. As far as I can tell, there is currently no way to check this.

Perhaps a command isSupported or fail an open with a new BadOpen?

[process-bot]

Thanks for the issue! Make sure it satisfies this checklist. My human colleagues will appreciate it!

Here is what to expect next, and if anyone wants to comment, keep these things in mind.