Hi there
The Observable way to achieve this is to use rxjs operators to combine two Observable streams into one. A typical operator for this is switchMap.
So, you are already having one stream _connection$, beautifully created using Subject. Now you need the other even stream to be of the same type, so you can switchMap them.
Ps. at least I believe switchMap does the trick. There are others, that behave differently pending on which stream triggered first and so on.