/**
     * This is a callback for application messages that you are sending to a
     * counterparty. If you throw a DoNotSend exception in this function, the
     * application will not send the message. This is mostly useful if the
     * application has been asked to resend a message such as an order that is
     * no longer relevant for the current market. Messages that are being resent
     * are marked with the PossDupFlag in the header set to true; If a DoNotSend
     * exception is thrown and the flag is set to true, a sequence reset will be
     * sent in place of the message. If it is set to false, the message will
     * simply not be sent. You may add fields before an application message
     * before it is sent out.
     * 
     * @param message
     *            QuickFIX message
     * @param sessionId
     *            QuickFIX session ID
     * @throws DoNotSend --
     *             This exception aborts message transmission
     */
    void toApp(Message message, SessionID sessionId) throws DoNotSend;