Provide connection/session failure callback.

[ecorm]

Consider providing a way to notify one or more observers when a connection is dropped or when the session is closed by the other peer.

[michaelaeriksen]

I have issues with dropped connections and currently the only way to fix is a restart of program at the moment. Any pointers of how to fix this?

[ecorm]

Sorry, I haven't yet put any thought in how I'd implement this. It's not an urgent feature for my project because Crossbar is hosted on the same device as my C++ program.