Research And Development Of OPC Technology And Communication Server Based On Overlapped I/O Model Of Event Notification

With the developing of computer technology,more and more software and hardware are used in industry control field and system integration becomes harder than before.So it is very necessary to use the same standard to communication for both user and vender.OPC(OLE for Process Control)is designed by OPC foundation for the communication and interoperability of all kinds of automation systems.It is base on the COM/DCOM and the XML technology and builds a set of standard communication interfaces,which makes automation system able to access data from hardware more quickly and efficiently.It also makes all parts of the system able to communicate to each other seamlessly and greatly improves the interoperability and flexibility of automation system.OPC XML-DA specification is the newest member of OPC family and it is designed for cross-platform applications on Internet.It makes the integrations of automation systems in plant floor with enterprise information management systems possible and opens a great new space for the development of OPC specifications.This paper describes the principal of OPC in detail.And the design and implement of OPC DA Server are also detailed explain in the paper.The software structure and implementation of OPC Server also explained in the paper.The server is more flexible and extendable by using the COM interfaces and object pointers.At the same time,also introduced the specification OPC XML-DA based on Web service technology.It is developed for the communication of different platforms and the applications based on Internet.A middle server is designed based on the specification OPC DA and OPC XML-DA.It makes the integration of control system in plant and enterprise information management system.The paper also introduces the principle of Overlapped I/O and Socket.A Communication Server,which is Based on Overlapped I/O,Event Notification, Socket and DCS,is developed.