which pgm is accessing the net?

[rikona]

Running 16.04 updated [yes - will be updating]. :-) My external hardware
firewall [firewalla] alerts me when it sees 'different' activity.
Getting several 'watching video" alerts re googlevideo.com. But, not
watching any video [that I know of]. Still have perhaps 50 pages or so
open in several browsers, which seems like a likely candidate, but all
ads, on-page videos, etc have been stopped.

Is there a way to find out exactly which pgm is accessing the net,
preferably with the net address it's using, and giving me the pgm pid?
If not, what's the best way to figure this out? 

I'd rather not shut down one little thing, wait a day or so to see if
it's stopped, then another little thing, and so on. I'd like something
faster, easier, and more precise, if possible.

Thanks