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Well galactic communication is one-way: every civilization reaching the tech level needed to participate in it just starts to send out everything they know, never hoping for anyone to reply. Additionally, every participating civilization starts relaying everything they hear from one side to the other side, so civilizations which are mutually out of range can hear from each other.

There is a galactic consent that nobody will ever be able to actually visit each other.

And of course, this is pure science fiction :)