It was Nikola Tesla who first came up with the idea of using transmission signals to contact Alien life forms in 1896.
Modern Mainstream Scientific research into the possibility of Extraterrestrial life is being conducted primarily with Radio Telescopes that are attempting exactly that.
Of course any response received doesn't have to be via something "alive" per se it just has to be "on purpose."
Some think we received something "On purpose" in 1977- this message has been dubbed "The Wow Signal."
Read about it on UniverseToday
Listen and watch the waveforms here:
More cool Radio Telescope stuff from SETI (Search for Extraterrestrial Intelligence)
We had another one just recently read about it on New Scientist.