There are several films with the title "Contact". Among them is a film based on the book by astronomer Carl Sagan. Anyone who has not seen this movie must see it.
This film faithfully shows the work of radio astronomers in the SETI project. The SETI project is the general name of projects and activities to search for extraterrestrial civilizations and possible contact with them. The prototype for the protagonist was radio astronomer Jill Tarter. There is a blind employee in the film and there is a blind software engineer in institute of SETI. Thus, the filmmakers were familiar with the real work of radio astronomers at the end of the 20th century. Within the SETI project, signals are searched in the radio range. We all know about the existence of electric rays and eels. Stingrays appeared at the very beginning of the Jurassic period of the Mesozoic era 200 million years ago.
A little later, electric eels appeared. Later, regardless of the stingrays, eels mastered electricity.
Fish have mastered electricity and used it successfully. Man mastered radio waves 100 years ago and rushed to use this archaic physics for contact with extraterrestrial intelligence. Probably even in the museums of developed civilizations there are no functioning radios left. Consequently, this approach is doomed to failure. However, science is developing and already now it is possible to change the way of searching for extraterrestrial intelligence.
You can take advantage of the discovery of quantum physics of entangled elementary particles. This branch of science is called nonlocal quantum physics. Suppose a civilization has reached the point where it can make its star generate entangled photons in the visible or infrared region of the light spectrum. There are two types of entanglement of photons: the polarization of the photons is parallel to each other; polarization of photons is perpendicular to each other. By modulating the streams of photons falling on the planet, you can modulate the streams of light coming in all directions from the star. To receive such signals, a telescope and a photodetector with a polarizer are required. However, such broadcasting will be carried out by a civilization that is slightly superior to ours. But what is the galactic connection of highly developed civilizations, then our imagination is not enough.