Well, if we do detect a signal, we're not going to just transmit "wassup?" and wait for an answer. I think it will be an interesting problem to have a conversation with other beings where the lag time is measured in decades!
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.
There is a galactic consent that nobody will ever be able to actually visit each other.
And of course, this is pure science fiction :)