For the client-server application over TCP, why must the server program be executed before the client program? For the client server application over UDP, why may the client program be executed before the server program?

Johnson enterprises uses a computer to handle its sales invoices. lately, business has been so good that it takes an extra 3 hours per night, plus every third saturday, to keep up with the volume of sales invoices. management is considering updating its computer with a faster model that would eliminate all of the overtime processing.