Method close_expected

src/websockets/protocol.py:517–558

Tell if the TCP connection is expected to close soon. Call this method immediately after any of the ``receive_*()``, ``send_close()``, or :meth:`fail` methods. If it returns :obj:`True`, schedule closing the TCP connection after a short timeout if the other

(self)

        return writes

    def close_expected(self) -> bool:
        """
        Tell if the TCP connection is expected to close soon.

        Call this method immediately after any of the ``receive_*()``,
        ``send_close()``, or :meth:`fail` methods.

        If it returns :obj:`True`, schedule closing the TCP connection after a
        short timeout if the other side hasn't already closed it.

        Returns:
            Whether the TCP connection is expected to close soon.

        """
        # During the opening handshake, when our state is CONNECTING, we expect
        # a TCP close if and only if the hansdake fails. When it does, we start
        # the TCP closing handshake by sending EOF with send_eof().

        # Once the opening handshake completes successfully, we expect a TCP
        # close if and only if we sent a close frame, meaning that our state
        # progressed to CLOSING:

        # * Normal closure: once we send a close frame, we expect a TCP close:
        #   server waits for client to complete the TCP closing handshake;
        #   client waits for server to initiate the TCP closing handshake.

        # * Abnormal closure: we always send a close frame and the same logic
        #   applies, except on EOFError where we don't send a close frame
        #   because we already received the TCP close, so we don't expect it.

        # If our state is CLOSED, we already received a TCP close so we don't
        # expect it anymore.

        # Micro-optimization: put the most common case first
        if self.state is OPEN:
            return False
        if self.state is CLOSING:
            return True
        if self.state is CLOSED:
            return False
        assert self.state is CONNECTING
        return self.eof_sent

    # Private methods for receiving data.