Recently, together with development of communications technology, monitoring and control systems have been used in many fields. When monitoring and control systems are developed, one of important things is considered about a redundancy so that the system can be operated normally whenever hardware faults are occurred partly.
In this paper, we introduce a monitoring and control system with a redundancy function for servers and networks. The system, therefore, has an active server and standby server. Each server also has 3 communication ports, and 2 ports are connected to all field units and 1 port is connected to another server. In fields, all field units have to be constructed 2 communication ports connected each server through communication lines. Also, each server's communication program is implemented by analyzing and handling fault elements, and is modularized for linking easily with a monitoring and control module. An experiment with 2 servers and 2 field units is constructed to demonstrate its effectiveness.