WatchOS 2.0: WCSessionDelegate not get called (in Simulator)

In general, it is not a good idea to receive WCSession data in a UIViewcontroller, since you never can be sure whether it is there or not.

Apple says you should start receiving as soon as possible. Your UIApplicationDelegate is a good place to receive data from WCSession and a good place to set it up as early as possible.

Edit

You also don't hold a reference to your activated session on the watch side. This means Apple can remove all the session ressources.

So you next call to defaultSession gets you a fresh unactivated session.

Edit 2

In my experience you have to do 2 things when testing the communication between WatchApp Extension and iOS App:

1. Start WatchApp from XCode 7 (sometimes I have to do this twice)
2. go into the iOS Simulator and start your iOS App manually

There may be more ways to make sure both run and can communicate.

Also try to send a message from iOS App to your WatchApp extension, this works for me.