I based my comment on the one that said "2 planets with intelligent lifeforms would've developed culturally and politically... if both civilizations grew at the same rate, 2 Galileos would've looked at the other planet and figured out "we have neighbors!"" I think that's quite a different situation than a deer or a crow attempting to make contact. It seems likely that if scientist in the 1600s were to figure out that there's life on the other planet, they're realize that the best way they could communicate would be visually. Then it would just be a matter of devising a large enough way to signal visually.