Understanding of OPC protocol

One 、OPC

OPC It's a way to use Microsoft COM/DCOM Technology to reach an agreement on automatic control ,

Use the typical C/S Pattern ,

in the light of The driver of the hardware device is completed by the hardware manufacturer , Provide unity OPC Interface standard Server Program ,

Software vendors only need to follow OPC Standard interface preparation Client The program accesses Server Program to read and write , Communication with hardware devices can be realized .

OPC The agreement includes ：

1. DA(Data Access) standard ： This specification is mainly used to access data
2. A&E(Alarm and Event) standard ： Based on events , Provide Client End subscription , After event triggering Server The data access method that the client actively submits back data .
3. HDA(History data access) standard
4. OPC XML-DA standard

Two 、OPC UA

OPC UA(Unified Architecture)：OPC A new version of the agreement , 

No longer bound to COM/DCOM technology , It means no longer like the traditional （Classic）OPC The agreement only supports in Windows Etc. on the platform , Cross platform , meanwhile OPC UA A reliable communication mechanism is also used