On Wed, 11 May 2016, Gisle Vanem via curl-users wrote:

> * ALPN, server did not agree to a protocol
>
> Not sure I understand why the ALPN "fails" in libcurl (Win-10/MSVC,
> OpenSSL/1.1.0). This "Application Layer Protocol Negotiation" works
> fine in my Google Chrome:
> Application Layer Protocol Negotiation Yes h2 spdy/3.1 http/1.1

Really? Neither Firefox nor Chrome on my Linux box negotiate h2 on
www.ssllabs.com for me!

> Is building with 'USE_NGHTTP2' required for this feature to work?

Well, it logs the output that it tries to use ALPN which means libcurl is
using it.

> The page:
> https://en.wikipedia.org/wiki/Application-Layer_Protocol_Negotiation
>
> says "It is used by HTTP/2". It doesn't says "HTTP/2" is required.

That's correct. ALPN is just a TLS extension for negotiating which protocol to
use "behind" TLS, so it could be used by just about any protocols. HTTP/2 is
the posted child for it though and is the protocol (version) the extension was
made for.

-- 
  / daniel.haxx.se
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