Why can i smell rotten eggs coming out of the floor drain in my basement ?

The smell is caused by methane buildup in the sewer pipes. The floor drain in your basement has a P-trap on it that is usually full of water, this stops the methane from coming out of the floor drain. The water in the P-Trap has evaporated allowing the sewer gasses to enter your house. Pour a few liters of water back down the floor drain to re-prime the trap , and the smell should go away.