PACiS GTW GTW/EN T/C40, Техническое руководство

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GTW/EN CT/C40 Communication
Page 52/64 PACiS Gateway
7.2 OPC Standard layer
This layer provides a way to access (read/write) to a set of data sources. The OPC Client
connects to the OPC Server and communicates to it through the OPC interfaces. The OPC
Server object provides functionality to the OPC client to create and manipulate group
objects. OPC Group objects allow the OPC Client to manage the data it wants to access.
The following sections deals with these interfaces and how they are implemented in the
toolkit. For a complete reference of the OPC Data Access interfaces see OPC Data Access
Custom Interface Standard version 2.05A.
7.2.1 OPCServer object
This is the only one COM object available from an OPC Client point of view. All the others
object will be created or accessed through the server. The set of interfaces provided by this
object includes:
- IOPCServer
- IOPCCommon
- IOPCBrowseServerAddressSpace
- IOPCItemProperties
- IOPCServerPublicGroups
- IOPCEventServer
- IConnectionPointContainer
IOPCServer interface:
This is the main interface of an OPC server. This interface is used to manage the group of
an OPC server (add, remove, browse, get). This interface is also used to get the current
status of an OPC server.
IOPCommon interface:
This interface is used to specify the localization of the CCOMOPCServer class. In the current
implementation of the class the only localization supported is the one of the machine the
sever is running on. This interface also enable the client to give its name to the server. It can
be useful to get a list of client from the toolkit.
IOPCBrowseServerAdressSpace interface:
This interface allows clients to get information about tags managed by servers.
Implementation lies on a COM object named CCOMOPCTagPtr. Each time a tag is created,
a CCOMOPCTagPtr is created and it keeps a reference on the tag. All the tag pointers are
linked together, either in a hierarchical way or in a flat way.
IOPCItemProperties interface:
This interface can be used by clients to browse the available properties associated with a tag
and to read the current values of theses properties.
IOPCServerPublicGroups interface:
This interface is used to create public groups. These groups can be share by many clients.
Standard group created by the AddGroup method of the IOPCServer interface is private to
the server which created it. With a public group many client can have access to the same
group of items.
IOPCEventServer interface:
This interface is used to manage the alarms and events functionality.