Chapter 1

Command Description
Terminate Stops game session. Valid in any state.
Resend Resend last RGCP response/request packet. Valid inRGCP initiating or
waiting states.
Receive all Initiates receive of any packets. Valid in any state except BSP blank.
Program Structure
In the Battleships program, the CGameController handles all the BSP protocol, including
functions called by the UI and RGCP handler functions. The controller also implements all
send-request and send- response functions implied by BSP and maintains state transitions
in accord with the design above.
A key aspect of the controller design is that every public function and many private functions
assert the validity of the requested operation, given current BSP and RGCP states. The app
UI and views are responsible for prechecking user-initiated commands, so that no invalid
command can be issued to the controller.
Taking BSP Forward
BSP combines a multigame session protocol with the specifics of the Battleships game. It
would be possible to separate these aspects into two layers.
A truly general protocol may or may not be worthwhile: other games could reuse BSP's
patterns without reusing its code. In any case, patterns differ between games. A game that
can be tied, for instance (as opposed to only won or lost), may require a different approach.
It would be possible to improve on the first-move selection here, by changing only the UI, to
select random first-move preferences. BSP itself would not have to be altered.
Summary
We've now seen TOGS components described in detail – with the exception of the Bluetooth
and SMS GDP protocol implementations that are described in Chapter 20.
The content of this appendix is heavier and more precise than that of many of the chapters
in this book. I wrote it before I wrote most of the code it describes, and have not changed it
substantially since – except that I've maintained some parts as the code has evolved. That's
a healthy (if unusual!) software engineering practice. In this case, doing the documentation
before the code saved me a lot of time.