The adult tomato horn worm is a large moth that can find tomato plants by scent. Here is a link to a description of the horn worm. You can defeat the horn worm by covering your plants with netting that doesn't admit the sphinx moth, a fairly large moth. There is a variety of netting on sale that admits various degrees of light. You need to look at 95-98% light admitting net.
Before you net, wash your tomato leaves and stems with insecticidal soap to get rid of eggs. I use net fruit bags on the tomato fruit and don't net my plants. Instead, I keep after the leaf eaters.