Support plain (non-SSL) connections

[ronkorving]

As discussed on Twitter, this is a remaining TODO for this module.
{ plain: true, ssl: false } is documented, but doesn't seem to do anything.

Reference: https://httpwg.github.io/specs/rfc7540.html#discover-http

[ronkorving]

So, @indutny, you mentioned the challenge is to implement upgrade response/request. I'm confused how HTTP/2 can even work without it, but can't find anything in the codebase to deal with upgrade requests. Does that mean that generally clients that support HTTP/2 will downgrade to HTTP/1.1 (instead of upgrading)?

Keep in mind, I'm new to HTTP/2. But am willing to give this a shot if nobody else will :)

[indutny]

@ronkorving it usually works on top of TLS, and there is ALPN TLS extension to negotiate the protocol ahead of time.

[ronkorving]

Got it, thanks. So it's for non-encrypted connections where UPGRADE becomes the method?

[indutny]

Yes, exactly!

[ronkorving]

Unfortunate that not a single browser seems to send Upgrade: h2c. Or am I doing something wrong here? I also tried returning an Alt-Svc: h2c=":8080" header as described here to advise that I support HTTP2, but it doesn't seem to have any effect.

[indutny]

Indeed. I can't find any reference of h2c in the chromium's source code. This is very sad.

[ronkorving]

:( looks like for now I'm screwed then. My Raspberry Pi will either have to put up with encrypting streams of video, or I need to give up on HTTP2 (which I need, because I run into browser connection limits otherwise)... Sigh :(