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By Root 1631 0

looking at it this time, notice how you can discover the message type by partially reading into the data stream. This is very useful since the message containing StateData is sent unreliably and the message containg MessageData is sent reliably:

- (void) receiveData:(NSData *)remoteData fromPeer:(NSString *)peer

inSession: (GKSession *)session context:(void *)context {

int messageType;

[remoteData getBytes:&messageType length:sizeof(int)];

if (messageType == 0) {

StateData paddleData;

[remoteData getBytes:&paddleData length:sizeof(StateData)];

// Remote player should display on top so we need

// to invert the values

paddleData.paddleLocation.x = 320 - paddleData.paddleLocation.x;

paddleData.paddleLocation.y = 480 - paddleData.paddleLocation.y;

mainView.topPaddleData = paddleData;

// if we are a client we need to copy puck data sent from the host

if (mainView.connectionType == CLIENT_CONNECTION ) {

[mainView updatePuckData:paddleData];

}

[self sendData];

}

else {

EventData eventData;

[remoteData getBytes:&eventData length:sizeof(EventData)];

[mainView displayMessage:SCORE_MESSAGE forPlayer:TOP_PLAYER];

}

}

Calling hockeyTableDidScore and showPeerPicker sends out the data we just saw being received in the method receiveData from the preceeding code:

- (void)hockeyTableDidScore:(PlayerCode)playerCode {

EventData eventData;

eventData.packetType = 1;

NSData *dataPacket = [[NSData alloc] initWithBytes:&eventData

length:sizeof(EventData)];

[session sendDataToAllPeers:dataPacket withDataMode:GKSendDataReliable

error:nil];

}

- (void)sendData {

if (mainView.connectionType == HEADTOHEAD_CONNECTION) return;

StateData paddleData = mainView.bottomPaddleData;

NSData *data = [[NSData alloc] initWithBytes:&paddleData

length:sizeof(StateData)];

[session sendDataToAllPeers :data withDataMode:GKSendDataUnreliable

error:nil];

}

Establishing a connection between peers

The following code to connect peers is almost identical to that in P2P Chat. However, one very important step stands out. The method session: didReceiveConnectionRequestFromPeer is used to make the distinction that we are the client if it is called (Listing 7.7).

Listing 7.7

Using the Peer Picker to Establish a Connection Between Peers

- (void)showPeerPicker {

// allocate and setup the peer picker controller

picker = [[GKPeerPickerController alloc] init];

picker.delegate = self;

picker.connectionTypesMask = GKPeerPickerConnectionTypeNearby;

[picker show];

}

- (void)peerPickerController:(GKPeerPickerController *)picker

didSelectConnectionType:(GKPeerPickerConnectionType)type {

if(type == GKPeerPickerConnectionTypeOnline) {

}

}

- (GKSession *) peerPickerController:(GKPeerPickerController *)picker

sessionForConnectionType:(GKPeerPickerConnectionType)type {

session = [[GKSession alloc] initWithSessionID:

@”com.yourwebsite.yourapplicationname” displayName:nil

sessionMode:GKSessionModePeer];

session.delegate = self;

return session;

}

- (void)peerPickerController:(GKPeerPickerController *)picker

didConnectToPeer:(NSString *)peerID {

[self.picker dismiss];

}

- (void)peerPickerControllerDidCancel:(GKPeerPickerController *)picker {

[self.picker dismiss];

[self.rootViewController showMenu];

}

- (void)session:(GKSession *)session

didReceiveConnectionRequestFromPeer:(NSString *)peerID {

connectionType = CLIENT_CONNECTION;

mainView.connectionType = CLIENT_CONNECTION;

}

- (void)session:(GKSession *)session peer:(NSString *)peerID

didChangeState:(GKPeerConnectionState)state {

switch (state) {

case GKPeerStateConnected:

[self.session setDataReceiveHandler :self withContext:nil];

[self.picker dismiss];

[self sendData];

break;

case GKPeerStateDisconnected:

break;

}

}

@end

Analyzing Business Aspects

Building an application like AmuckPuck can be a rewarding venture, but it comes with a cost. Bringing together the many technologies can lead to a lot of