httptest.py

from socket import create_connection
from ssl import create_default_context

def run_test(addr, httpversion):
    host, port = addr
    ctx = create_default_context()
    with create_connection(addr) as s:
        with ctx.wrap_socket(s, server_hostname=host) as ss:
            ss.send(b'GET /robots.txt %s\r\n' % httpversion.encode('utf8'))
            ss.send(b'Host: %s\r\n' % host.encode('utf8'))
            ss.send(b'\r\n')
            line = ss.read(1024)
            lines = line.split(b'\r\n', 1)
            if len(lines) != 2:
                return None
            parts = lines[0].split(b' ')
            if len(parts) != 3:
                return None
            try:
                return int(parts[1])
            except:
                return None

tests = [
    'HTTP/0',
    'HTTP/1',
    'HTTP/2',
    'HTTP/x',
    'HTTP/0.0',
    'HTTP/1.0',
    'HTTP/1.1',
    'HTTP/1.9',
    'HTTP/2.0',
    'HTTP/9.1',
    'HTTP/x.x',
    'HTTP/0.00',
    'HTTP/1.00',
    'HTTP/1.99',
    'HTTP/1.999',
    'HTTP/1.9999',
    'HTTP/12.0',
    'HTTP/123.0',
]

addr = ('github.com', 443)

for test in tests:
    status = run_test(addr, test)
    if status is None:
        print(test, '*')
    else:
        print(test, status)