In the Summer of 1977 radio astronomers at Ohio State University recorded the famous Wow Signal, a strong narrowband signal that remains an enigma of SETI work to this day.
Analysis of this single data point has probably saturated in the decades since, and of course nothing else like it has popped up again. Indeed it may be that radio communication is generally infeasible across the cosmic dimensions, as the interval when a civilization might use radio is too short for round-trip conversations via electromagnetic mechanisms.
Perhaps they graduate to something much more “advanced” or even, more rapid. Obviously that’s not something within the bounds of our current physical worldview. Maybe that’s not an accident either, after all when was the last time you had a meaningful cell-phone conversation with your dog?
So it could be that our possible cohort of cosmic chat buddies is restricted to those somewhere in a range of technological sophistication that overlaps our own by maybe a couple hundred years or so, who are also within a couple hundred light years and who are barking loudly in our direction. That probably narrows the possibilities down, somewhat, even in a Really Big Universe.
The recent BBC/Discovery Channel episode of Into the Universe with Stephen Hawking included a short, cursory and somewhat unsatisfactory piece on the Wow Signal, which is a shame. That kind of venue can reach a lot of people looking for a bit of wonder, and the Wow Signal is wonder on a stick. With sprinkles.