Method process_request

src/websockets/server.py:205–275

Check a handshake request and negotiate extensions and subprotocol. This function doesn't verify that the request is an HTTP/1.1 or higher GET request and doesn't check the ``Host`` header. These controls are usually performed earlier in the HTTP request handling co

(
        self,
        request: Request,
    )

        return Response(101, "Switching Protocols", headers)

    def process_request(
        self,
        request: Request,
    ) -> tuple[str, str | None, str | None]:
        """
        Check a handshake request and negotiate extensions and subprotocol.

        This function doesn't verify that the request is an HTTP/1.1 or higher
        GET request and doesn't check the ``Host`` header. These controls are
        usually performed earlier in the HTTP request handling code. They're
        the responsibility of the caller.

        Args:
            request: WebSocket handshake request received from the client.

        Returns:
            ``Sec-WebSocket-Accept``, ``Sec-WebSocket-Extensions``, and
            ``Sec-WebSocket-Protocol`` headers for the handshake response.

        Raises:
            InvalidHandshake: If the handshake request is invalid;
                then the server must return 400 Bad Request error.

        """
        headers = request.headers

        connection: list[ConnectionOption] = sum(
            [parse_connection(value) for value in headers.get_all("Connection")], []
        )
        if not any(value.lower() == "upgrade" for value in connection):
            raise InvalidUpgrade(
                "Connection", ", ".join(connection) if connection else None
            )

        upgrade: list[UpgradeProtocol] = sum(
            [parse_upgrade(value) for value in headers.get_all("Upgrade")], []
        )
        # For compatibility with non-strict implementations, ignore case when
        # checking the Upgrade header. The RFC always uses "websocket", except
        # in section 11.2. (IANA registration) where it uses "WebSocket".
        if not (len(upgrade) == 1 and upgrade[0].lower() == "websocket"):
            raise InvalidUpgrade("Upgrade", ", ".join(upgrade) if upgrade else None)

        try:
            key = headers["Sec-WebSocket-Key"]
        except KeyError:
            raise InvalidHeader("Sec-WebSocket-Key") from None
        except MultipleValuesError:
            raise InvalidHeader("Sec-WebSocket-Key", "multiple values") from None
        try:
            raw_key = base64.b64decode(key.encode(), validate=True)
        except binascii.Error as exc:
            raise InvalidHeaderValue("Sec-WebSocket-Key", key) from exc
        if len(raw_key) != 16:
            raise InvalidHeaderValue("Sec-WebSocket-Key", key)
        accept_header = accept_key(key)

        try: