Chapter 1

Here's part of the controller code that runs when the player using that controller requests a
hit to a square on their opponent's fleet:
void CGameController::ViewCmdHitFleet(TInt aX, TInt aY)
{
__ASSERT_ALWAYS(!(iEngine->iOppFleet.IsKnown(aX, aY)), Panic
(EHitFleetAlreadyKnown));
// hit fleet
iEngine->iOppFleet.SetShipType(aX, aY, iEngine-
>iMyFleet.ShipType
(aX, aY));
TFleet::THitResult result = (TFleet::THitResult)iEngine->
iOppFleet.SetHit(aX,aY);
iEngine->iMyFleet.SetHit(aX,aY);
// update view and play sounds
-
}
The purpose of this code is to:
� find out what was on the opponent's fleet on that square,
� mark the information as found on my view of the opponent's fleet,
� mark the opponent's fleet as hit on that square.
The code simply follows pointers to find the opponent's real fleet:
TFleet& oppFleet = iOtherController->iGameEngine->iMyFleet;
Then, the code calls functions on both my view of the opponent's fleet, and on the
opponent's fleet itself.
From a design point of view, this is all very elegant. I was able to reuse the same engine and
view in Battleships, and testing them here just involved the plumbing above.
16.2.3 Communications is Different
But this implementation of CGameController::ViewCmdHitFleet() simply won't do in
a real communications world. It uses a synchronous, reliable function call, with parameters in
internal format, to find out the state of my opponent's fleet, and to inform my opponent that I
have hit a square.
With real communications, I have to tackle some fundamental issues:
� Communications is asynchronous. I might have to wait an arbitrary time between
sending the hit request, and receiving the response. While I'm waiting, I might change
my mind and decide to abandon the game. So, while I am waiting for the response from
the other player, the game must be able to handle other kinds of input from me.
� Communications is unreliable. I need to use protocols that ensure that either my
message gets to the other player, or that I am reliably informed that it has not got there
for a reason that I can understand. I may need to be able to retry sending my message.
� Communications uses external formats. I will have to decide on the binary format that I
use to communicate between the two games. I will have to change to external format
when sending, and change back into internal format when receiving data. Furthermore,
if I wish to play this game against an implementation running on a non-Symbian OS