Twisted webserver with plain http2 (h2c) - twisted

Question

Twisted supports http1 + http2.
How to setup a twisted http2 server over TCP (neither ALPN nor protocol-upgrade)?
The server should answer to this query:
curl --http2-prior-knowledge http://localhost:8000/

Answer 1

Twisted should set up HTTP/2 servers for you auto-magically. Make sure you install twisted's http2 modules. The simplest way is to use pip:
pip install -U twisted[http2]
However, I've noticed a few times that it doesn't do run the HTTP/2 stuff out of the box. I had to uninstall h2, hyper and hyperframe, then reinstall them.
pip uninstall h2 hyperframe hyper
pip install -U twisted[http2]
Using a self signed certificate, here's a small klein webserver example.
openssl genrsa -aes256 -passout pass:SuperSecretPassword -out server.key 4096
openssl req -new -key server.key -passin pass:SuperSecretPassword -out server.csr
# Common Name (e.g. server FQDN or YOUR name) []:localhost
openssl x509 -req -passin pass:SuperSecretPassword -days 365 -in server.csr -signkey server.key -out server.crt
openssl rsa -in server.key -out server_no_pass.key -passin pass:SuperSecretPassword
mv server_no_pass.key server.key
cat server.crt server.key > selfsigned.pem
rm server.crt server.csr server.key
from klein import route, run
#route("/")
def hello(req):
if req.clientproto == b"HTTP/2":
return "http2"
return "http1.1"
run(endpoint_description="ssl:8000:privateKey=selfsigned.pem")
Update
While it's not best practice, there's nothing prohibiting you from running HTTP/2 server on a non-TLS connection. I believe most browsers won't support a non-TLS HTTP/2 server though (at least I couldn't get Firefox and Chrome to work with it). Twisted won't work out the box for you either, so that means you'll have to implement your own server. Follow the twisted example on the hyper-h2 site. Then replace endpoints.SSL4ServerEndpoint with endpoints.TCP4ServerEndpoint.
# ...
endpoint = endpoints.TCP4ServerEndpoint(reactor, 8080, backlog=128)
endpoint.listen(H2Factory(root))
reactor.run()