By "the other types" I also mean HTTP/1.1 over plain TCP and over TLS.

Yes, it supports upgrade to http2. Here is an example with the nghttp
client:

nghttp2/src/nghttp -nvu http://nghttp2.org

[0.282] HTTP Upgrade request

GET / HTTP/1.1

Host: nghttp2.org

Connection: Upgrade, HTTP2-Settings

Upgrade: h2c-14

HTTP2-Settings: AAMAAABkAAQAAP__

Accept: */*

User-Agent: nghttp2/0.6.3-DEV

[0.563] HTTP Upgrade response

HTTP/1.1 101 Switching Protocols

Connection: Upgrade

Upgrade: h2c-14

[0.563] HTTP Upgrade success
...

And if I use plain http:// URL, I get no answer on the client side and the
server returns "Received bad connection preface".

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Received on 2014-10-04