def websocket_handshake(security_key=None, origin=None, proto=None):
    """Waits for websocket handshake.

    :param str|unicode security_key: Websocket security key to use.

    :param str|unicode origin: Override ``Sec-WebSocket-Origin``.

    :param str|unicode proto: Override ``Sec-WebSocket-Protocol``.

    :rtype: None

    :raises IOError: If unable to complete handshake.
    """
