Can't send HTTP/2 request with curl

I install curl with support http2.0 protocol, and i see HTTP2 in version info.

$ ./curl --version
curl 7.42.1 (x86_64-apple-darwin14.5.0) libcurl/7.42.1 OpenSSL/1.0.2a zlib/1.2.5 nghttp2/0.7.13
Protocols: dict file ftp ftps gopher http https imap imaps ldap ldaps pop3 pop3s rtsp smb smbs smtp smtps telnet tftp 
Features: IPv6 Largefile NTLM NTLM_WB SSL libz TLS-SRP HTTP2 UnixSockets

But when i send a request via curl (with verbose mode), i see http1.1 protocol.

./curl -v --http2 https://http2bin.org/get
*   Trying 104.131.161.90...
* Connected to http2bin.org (104.131.161.90) port 443 (#0)
* ALPN, offering h2-14
* ALPN, offering http/1.1
* Cipher selection: ALL:!EXPORT:!EXPORT40:!EXPORT56:!aNULL:!LOW:!RC4:@STRENGTH
* successfully set certificate verify locations:
*   CAfile: /usr/local/etc/openssl/cert.pem
  CApath: none
* TLSv1.2, TLS Unknown, Unknown (22):
* TLSv1.2, TLS handshake, Client hello (1):
* SSLv2, Unknown (22):
* TLSv1.2, TLS handshake, Server hello (2):
* SSLv2, Unknown (22):
* TLSv1.2, TLS handshake, CERT (11):
* SSLv2, Unknown (22):
* TLSv1.2, TLS handshake, Server key exchange (12):
* SSLv2, Unknown (22):
* TLSv1.2, TLS handshake, Server finished (14):
* SSLv2, Unknown (22):
* TLSv1.2, TLS handshake, Client key exchange (16):
* SSLv2, Unknown (20):
* TLSv1.2, TLS change cipher, Client hello (1):
* SSLv2, Unknown (22):
* TLSv1.2, TLS handshake, Finished (20):
* SSLv2, Unknown (20):
* TLSv1.2, TLS change cipher, Client hello (1):
* SSLv2, Unknown (22):
* TLSv1.2, TLS handshake, Finished (20):
* SSL connection using TLSv1.2 / ECDHE-RSA-AES256-GCM-SHA384
* ALPN, server accepted to use h2-14
* Server certificate:
*    subject: OU=Domain Control Validated; OU=EssentialSSL; CN=www.http2bin.org
*    start date: 2015-02-21 00:00:00 GMT
*    expire date: 2016-02-21 23:59:59 GMT
*    subjectAltName: http2bin.org matched
*    issuer: C=GB; ST=Greater Manchester; L=Salford; O=COMODO CA Limited; CN=COMODO RSA Domain Validation Secure Server CA
*    SSL certificate verify ok.
* Using HTTP2
* Using HTTP2
* SSLv2, Unknown (23):
* SSLv2, Unknown (23):
* SSLv2, Unknown (23):
> GET /get HTTP/1.1
> Host: http2bin.org
> User-Agent: curl/7.42.1
> Accept: */*
> 
* http2_recv: 16384 bytes buffer
* SSLv2, Unknown (23):
* SSLv2, Unknown (23):
* http2_recv: 16384 bytes buffer
* SSLv2, Unknown (23):
* http2_recv: 16384 bytes buffer
* SSLv2, Unknown (23):
< HTTP/2.0 200
< server:h2o/1.6.1
< date:Wed, 03 Feb 2016 15:44:23 GMT
< content-type:application/json
< access-control-allow-origin:*
< access-control-allow-credentials:true
< x-clacks-overhead:GNU Terry Pratchett
< content-length:252
< 
{
  "args": {}, 
  "headers": {
    "Accept": "*/*", 
    "Connection": "keep-alive", 
    "Host": "http2bin.org", 
    "User-Agent": "curl/7.42.1", 
    "Via": "2 http2bin.org"
  }, 
  "origin": "193.238.96.12", 
  "url": "https://http2bin.org/get"
}
* Connection #0 to host http2bin.org left intact

Now cURL send request via HTTP/1.1

And if i set the --http1.0 option, then cURL send a request via HTTP/1.0.

Why cURL not send request via HTTP/2.0?

Operation system: OS X Yosemite (10.10.5).

Install cURL and OpenSSL via HomeBrew.

Thank.

Solution

It actually both sends and receives HTTP/2 already (draft-14 version, which is a pre-release version of the spec). You should consider upgrading your curl and nghttp2 libraries to get it to speak the final version of the HTTP/2 protocol (RFC 7540).

Hint from the server:

* ALPN, server accepted to use h2-14

curl shows the request using HTTP/1-style to make it look familiar but under the hood it converts it to HTTP/2 and sends it off.

The server then responds with HTTP/2:

< HTTP/2.0 200
< server:h2o/1.6.1
< date:Wed, 03 Feb 2016 15:44:23 GMT
< content-type:application/json
< access-control-allow-origin:*
[snip]