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# -*- coding: utf-8 -*-
"""
Server Plaintext Upgrade
~~~~~~~~~~~~~~~~~~~~~~~~
This example code fragment demonstrates how to set up a HTTP/2 server that uses
the plaintext HTTP Upgrade mechanism to negotiate HTTP/2 connectivity. For
maximum explanatory value it uses the synchronous socket API that comes with
the Python standard library. In product code you will want to use an actual
HTTP/1.1 server library if possible.
This code requires Python 3.5 or later.
"""
import h2.config
import h2.connection
import re
import socket
def establish_tcp_connection():
"""
This function establishes a server-side TCP connection. How it works isn't
very important to this example.
"""
bind_socket = socket.socket()
bind_socket.bind(('', 443))
bind_socket.listen(5)
return bind_socket.accept()[0]
def receive_initial_request(connection):
"""
We're going to receive a request. For the sake of this example, we're going
to assume that the first request has no body. If it doesn't have the
Upgrade: h2c header field and the HTTP2-Settings header field, we'll throw
errors.
In production code, you should use a proper HTTP/1.1 parser and actually
serve HTTP/1.1 requests!
Returns the value of the HTTP2-Settings header field.
"""
data = b''
while not data.endswith(b'\r\n\r\n'):
data += connection.recv(8192)
match = re.search(b'Upgrade: h2c\r\n', data)
if match is None:
raise RuntimeError("HTTP/2 upgrade not requested!")
# We need to look for the HTTP2-Settings header field. Again, in production
# code you shouldn't use regular expressions for this, but it's good enough
# for the example.
match = re.search(b'HTTP2-Settings: (\\S+)\r\n', data)
if match is None:
raise RuntimeError("HTTP2-Settings header field not present!")
return match.group(1)
def send_upgrade_response(connection):
"""
This function writes the 101 Switching Protocols response.
"""
response = (
b"HTTP/1.1 101 Switching Protocols\r\n"
b"Upgrade: h2c\r\n"
b"\r\n"
)
connection.sendall(response)
def main():
"""
The server upgrade flow.
"""
# Step 1: Establish the TCP connection.
connection = establish_tcp_connection()
# Step 2: Read the response. We expect this to request an upgrade.
settings_header_value = receive_initial_request(connection)
# Step 3: Create a H2Connection object in server mode, and pass it the
# value of the HTTP2-Settings header field.
config = h2.config.H2Configuration(client_side=False)
h2_connection = h2.connection.H2Connection(config=config)
h2_connection.initiate_upgrade_connection(
settings_header=settings_header_value
)
# Step 4: Send the 101 Switching Protocols response.
send_upgrade_response(connection)
# Step 5: Send pending HTTP/2 data.
connection.sendall(h2_connection.data_to_send())
# At this point, you can enter your main loop. The first step has to be to
# send the response to the initial HTTP/1.1 request you received on stream
# 1.
main_loop()
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