PURPOSE: To provide a network system which can improve the install work efficiency and can support a communication protocol.

CONSTITUTION: When the address information of a network interface device 100 and an intelligent device is not stored, a control means 110C of the network interface device 100 sends the setting request of the respective kinds of address information to a non-intelligent device 150 while referring to an address storage means 110B. The non-intelligent device sets the address information of the transmission source and the transmission destination by using a setting means 151D and the control means 110C establishes connection and transfers data based on the respective kinds of set address information, information corresponding to the communication protocol stored in a main storage means 110A and information for exchanging data with the intelligent device.