In a communication system of the present invention, second setting information is automatically generated according to first setting information used for performing predetermined processing between atleast two devices when the first setting information is set to a first device of the at least two devices, where the second setting information is generated for a second device of the at least two devices. Then, the communication system transmits the automatically-generated second setting information to the second device. Otherwise, the communication system writes the automatically-generated second setting information onto a portable recording medium so that the second device can read the second setting information from the portable recording medium.