This program emits sound at a frequency that is somewhere between 16,000Hz and 20,000Hz, that can't be heard by the human ear, and that is really bothering for the mosquitos. This is how the application works to get them out of the room.
If when you launch the application it seems as if nothing is happening, don't worry, that is normal. Anti Mosquitos is a lightweight application that, without requiring installation, stays active in the background emitting sound in the aforementioned frequency, that will manage that the mosquitos go somewhere else to feed.
We can't guarantee that it works 100%, but since it's free you have nothing to lose, try out Anti Mosquitos.