How to transfer data between phones over GKSession

I'm trying to create an app that transfers data between 2+ phones using GKSession. Thing is there are two options:

First: using the GKPeerPicker.. However here I get stuck at the point where I have to implement my own WIFI interface.. apple provides no instructions on how to do that:

- (void)peerPickerController:(GKPeerPickerController *)picker didSelectConnectionType:    (GKPeerPickerConnectionType)type {
    if (type == GKPeerPickerConnectionTypeOnline) {
        picker.delegate = nil;
        [picker dismiss];
        [picker autorelease];
       // Implement your own internet user interface here.
    }
}

Second: Skipping GKPeerPicker and doing the whole thing my self, like in this example. However the app dev documentation doesn't provide any instructions on how to send/receive data without using GKPeerPicker.. (nor could I find any example of that on thew web)

I just figured out how to connect devices without the peerpicker. It was a bit of a guessing game because the documentation is pretty unclear and I've looked for so long on the internet for any info about this. I'll try to explain everything here to clear up any questions anyone in the future might have.

From the documentation:

A GKSession object provides the ability to discover and connect to nearby iOS devices using Bluetooth or Wi-fi.

This was the first step to understand it for me. I thought the GKPeerPickerController was responsible of the advertising and connecting but GKSession actually does all that.

The second thing to understand is that what is referred to as peers are not necessarily connected to you. They can just be nearby waiting to be discovered and connected to. All peers have a state

GKPeerStateAvailable (this is what's useful!)
GKPeerStateUnavailable
GKPeerStateConnected
GKPeerStateDisconnected
GKPeerStateConnecting

So how do we actually connect? Well first we have to create a GKSession object to be able to find peers around us and see when they become available:

// nil will become the device name
GKSession *gkSession = [[GKSession alloc] initWithSessionID:@"something.unique.i.use.my.bundle.name" displayName:nil sessionMode:GKSessionModePeer];
[gkSession setDataReceiveHandler:self withContext:nil];
gkSession.delegate = self;
gkSession.available = YES; // I'm not sure this if this is the default value, this might not be needed

Now we have some delegate calls to respond to. session:didReceiveConnectionRequestFromPeer: and session:peer:didChangeState (you should also handle the calls of GKSessionDelegate for disconnection and failure appropriately)

-(void)session:(GKSession *)session peer:(NSString *)peerID didChangeState:(GKPeerConnectionState)state
{
    if(state == GKPeerStateDisconnected)
    {
        // A peer disconnected
    }
    else if(state == GKPeerStateConnected)
    {   
        // You can now send messages to the connected peer(s)
        int number = 1337;
        [session sendDataToAllPeers:[NSData dataWithBytes:&number length:4] withDataMode:GKSendDataReliable error:nil];
    }
    else if (state == GKPeerStateAvailable)
    {
        // A device became available, meaning we can connect to it. Lets do it! (or at least try and make a request) 
        /*
        Notice: This will connect to every iphone that's nearby you directly. 
        You would maybe want to make an interface similar to peerpicker instead
        In that case, you should just save this peer in a availablePeers array and 
        call this method later on. For your UI, the name of the peer can be 
        retrived with [session displayNameForPeer:peerId]
        */
        [session connectToPeer:peerID withTimeout:10];
    }

}

The other peer now received a request that he should respond to.

-(void)session:(GKSession *)session didReceiveConnectionRequestFromPeer:(NSString *)peerID
{
    // We can now decide to deny or accept
    bool shouldAccept = YES;
    if(shouldAccept)
    {
        [session acceptConnectionFromPeer:peerID error:nil];
    }
    else
    {
        [session denyConnectionFromPeer:peerID];
    }
}

Finally to receive our little 1337 message

-(void)receiveData:(NSData *)data fromPeer:(NSString *)peer inSession:(GKSession*)session context:(void *)context
{
    int number = 1337;
    if([data isEqualToData:[NSData dataWithBytes:&number length:4]])
    {
        NSLog(@"Yey!");
    }
}