Standalone version of the server started by `python3 -m http.server`

server.py

"""
A standalone version of the server started by `python3 -m http.server`.
Copied from Python 3.9 source.
"""
import contextlib
from functools import partial
import http.server
import os
import socket

if __name__ == '__main__':
    import argparse

    parser = argparse.ArgumentParser()
    parser.add_argument('--cgi', action='store_true',
                       help='Run as CGI Server')
    parser.add_argument('--bind', '-b', metavar='ADDRESS',
                        help='Specify alternate bind address '
                             '[default: all interfaces]')
    parser.add_argument('--directory', '-d', default=os.getcwd(),
                        help='Specify alternative directory '
                        '[default:current directory]')
    parser.add_argument('port', action='store',
                        default=8000, type=int,
                        nargs='?',
                        help='Specify alternate port [default: 8000]')
    args = parser.parse_args()
    if args.cgi:
        handler_class = http.server.CGIHTTPRequestHandler
    else:
        handler_class = partial(http.server.SimpleHTTPRequestHandler,
                                directory=args.directory)

    # ensure dual-stack is not disabled; ref #38907
    class DualStackServer(http.server.ThreadingHTTPServer):
        def server_bind(self):
            # suppress exception when protocol is IPv4
            with contextlib.suppress(Exception):
                self.socket.setsockopt(
                    socket.IPPROTO_IPV6, socket.IPV6_V6ONLY, 0)
            return super().server_bind()

    http.server.test(
        HandlerClass=handler_class,
        ServerClass=DualStackServer,
        port=args.port,
        bind=args.bind,
    )