The SETI program, or the Search for Extraterrestrial Intelligence program has been looking for alien civilizations for decades now, and has had no luck finding anything. Why is that? Is it because we truly are alone, or is it because we just don't have the means to contact them, or the knowledge of how to speak to them. Do aliens exist out there, and if they do, do they wish to contact us back? Are alien beings hiding from us, or have we just failed to be able to communicate with them?
The expanses of space are vast, and you can't just pick up a phone and call an alien. There are special ways that we have to go about looking for aliens, and other civilizations. We have to use such things like radio waves, and lasers to send our messages the millions of miles it may take for a our message to be received by an alien. Even then, we might not be able to even reach anyone, because the medium used to send these messages will fade away after awhile.
A radio wave would fizzle out somewhere in the solar system, meaning that unless there is a civilization on Jupiter that is using radio, it isn't going to hear us really well. A laser is better, but another civilization would have to be looking for beams of light coming from Earth, which is like looking for a needle in haystack in cosmic terms. If we are going to contact an alien civilization, it might have to come from them, instead of us. It clearly takes more technology than we have at this point.
Even if we can get our message to another civilization, how do we make our conversation meaningful? We could always use math, as that seems to be the language of the cosmos, but what if aliens don't use math? Maybe they have other ways of expressing a mile, or how to find the right angle of a triangle. What about the language barriers then? What if we don't find a way to speak with them, or communicate with them? What if we mistakenly start a war?
We can also communicate through pictures, and through videos if we ever contacted an alien species. The Voyager probes have pictures of humans on them, and other symbols showing where we are in the solar system. Even that though could be tricky, because how would we know who had contacted us, even if we saw a picture of them? What if they came from a planet we did not know about? I can pick up a picture of a person, and still not know where they came from, or who they are. Imagine if it was a picture from another world?
Contacting another civilization is going to be a long time coming. Space is simply too big, and we can't scope it all out fast enough for us to hear back in our lifetime, unless the aliens come to us. I think it would be interesting to see how we would cope, especially if the aliens were more advanced than we were.