Iphone – GKPeerStateAvailable for non existing peers

It's certainly possible to develop on a Windows machine, in fact, my first application was exclusively developed on the old Dell Precision I had at the time :)

There are three routes;

1. Install OSx86 (aka iATKOS / Kalyway) on a second partition/disk and dual boot.
2. Run Mac OS X Server under VMWare (Mac OS X 10.7 (Lion) onwards, read the update below).
3. Use Delphi XE4 and the macincloud service. This is a commercial toolset, but the component and lib support is growing.

The first route requires modifying (or using a pre-modified) image of Leopard that can be installed on a regular PC. This is not as hard as you would think, although your success/effort ratio will depend upon how closely the hardware in your PC matches that in Mac hardware - e.g. if you're running a Core 2 Duo on an Intel Motherboard, with an NVidia graphics card you are laughing. If you're running an AMD machine or something without SSE3 it gets a little more involved.

If you purchase (or already own) a version of Leopard then this is a gray area since the Leopard EULA states you may only run it on an "Apple Labeled" machine. As many point out if you stick an Apple sticker on your PC you're probably covered.

The second option is more costly. The EULA for the workstation version of Leopard prevents it from being run under emulation and as a result, there's no support in VMWare for this. Leopard server, however, CAN be run under emulation and can be used for desktop purposes. Leopard server and VMWare are expensive, however.

If you're interested in option 1) I would suggest starting at Insanelymac and reading the OSx86 sections.

I do think you should consider whether the time you will invest is going to be worth the money you will save though. It was for me because I enjoy tinkering with this type of stuff and I started during the early iPhone betas, months before their App Store became available.

Alternatively, you could pick up a low-spec Mac Mini from eBay. You don't need much horsepower to run the SDK and you can always sell it on later if you decide to stop development or buy a better Mac.

Update: You cannot create a Mac OS X Client virtual machine for OS X 10.6 and earlier. Apple does not allow these Client OSes to be virtualized. With Mac OS X 10.7 (Lion) onwards, Apple has changed its licensing agreement in regards to virtualization. Source: VMWare KnowledgeBase

There are two ways to do this.

The first way uses GameKit API. You start by having two separate classes, one that implements the GKSessionDelegate protocol and acts as a GameKit/Bluetooth "handler" and the other as the presentation UI (most likely some sort of viewcontroller with a tableview). The way you would wire it up is the handler manages the GameKit notifications etc and then calls delegate methods on the UI to update the table view when a peer connects/drops off, etc. That way, as devices come and go, your picker list should update to show who's around.

Below is some code to get you started:

- (BOOL) startPeer
{
    BOOL result = NO;

    if (!_session) {
        _session = [[GKSession alloc] initWithSessionID:BLUETOOTHSESSION 
                                                displayName:nil 
                                                sessionMode:GKSessionModePeer];
        _session.delegate = self;
        [_session setDataReceiveHandler:self withContext:nil];
        _session.available = YES;
    result = YES;
    }
    return result;
}

- (void) stopPeer
{
    // Set up the session for the next connection
    //
    [_session disconnectFromAllPeers];
    _session.available = YES;

    [self cleanupProgressWindow];
}

- (void) loadPeerList 
{
    self.peerList = [[NSMutableArray alloc] initWithArray:[_session peersWithConnectionState:GKPeerStateAvailable]];
}


- (void)session:(GKSession *)session peer:(NSString *)peerID didChangeState:(GKPeerConnectionState)state
{
    BOOL peerChanged = NO;

    switch(state) {

        // When peer list changes, we adjust the available list
        //
        case GKPeerStateAvailable:
            if (_peerList) {
                [_peerList addObject:peerID];
                peerChanged = YES;
            }
            break;

        // When peer list changes, we adjust the available list
        //
        case GKPeerStateUnavailable:
            if (_peerList) {
                [_peerList removeObject:peerID];
                peerChanged = YES;
            }
            break;


        // Called when the peer has connected to us.
        //
        case GKPeerStateConnected:
                    // start reading and writing
            break;

        case GKPeerStateDisconnected:
        {
            if (_isWriter) {
                _isConnected = NO;
                _deviceToSend = nil;
                [self cleanupProgressWindow];
            } else {
                // Other side dropped, clean up local data and reset for next connection
                self.dataRead = nil;
            }
        }
            break;
    }

    // Notify peer list delegate that the list has changed so they can update the UI
    //
    if (peerChanged)
        CALLDELEGATE(_peerListDelegate, peerListChanged);           
}

The second way to do it is to use standard Bonjour service selection mechanisms. GameKit is implemented on top of Bonjour (but over Bluetooth instead of WiFi) so once the two sides have gone through network reachability with each other and connected they are registered under Bonjour and act like any Bonjour service would. The GameKit way is probably a little easier, but if you already have code for WiFi it can be reused for Bluetooth as well.