I am writing mutliplayer game and thought I would create two instances of GKSession. One session set to GKSessionModeServer and the other to GKSessionModeClient. The server is properly reported when I call peersWithConnectionState: on the client peer and each session has different peer ids. But when I try to connect to the server I receive the message session:connectionWithPeerFailed:withError: with the error description "Failed while pending outgoing invitation.".
Using two GKSessions works when Wi-Fi is available. I am afraid that there is some limitation with Bluetooth that disallows this but I am not sure. I could rewrite the code to use a single GKSession on the server but I would rather not code special cases if I know that someone else got it working with two instances.
If I turn off both Wi-Fi and Bluetooth i get the error "Network not available." which I don't get if either is turned on. This makes me believe it won't work when there is another iPhone is nearby either.
I rewrote the code so I only create one GKSession on the hosting device and send data between the server and the local client directly without using the GKSession. I could finally test this with two devices and they properly connect to each other. So the lesson is to have only one GKSession on the host and it will work with Bluetooth as well as Wi-Fi.