Disconnection detection appears to be inconsistent

[cespare]

On my mac, if I disconnect the network Prat never reports that it's disconnected. If I send messages, they just don't show up. However, when I reconnect the internet, any messages that were sent in the meantime do appear.

I'm not sure if it's possible, but we should really figure this case out and report disconnection. At least, we should know that this is happening if we stop hearing PONGs when we send PINGs.