Tips for Integrating with an OPC client
75
Building Technologies
048_DMS_MK8000_ICC_MP4.30_A6V10062407_a_en
Fire Safety & Security Products
06.2010
On a workgroup network, on the servers and clients an account with the
same username/password combination must be created;
Check DCOM settings according to the next section.
For more details, see the Integration tips section of the MK8000 Installation Con-
figuration and Commissioning guide.
Modifying DCOM settings
OPC security is based on the Microsoft Distributed Component Object Model
(DCOM), which may affect access to all DCOM based Windows applications.
Therefore, the default security settings that you select for the OPC server, FEP,
and client machines will affect all DCOM based applications, regardless of whether
they are part of OPC or not.
Setting up a DCOM connection between two computers means setting up the sta-
tions so that they have permission to access each other. This is a two way street.
The client must have permissions to access the machine with the OPC server and
vice versa. If you don't have permissions set both ways, then the machines will not
communicate correctly.
There are three major types of permissions:
Access:
These permissions allow a client machine to connect to a server, retrieve a list
of OPC servers, and connect to an OPC server application.
They also allow the OPC server to make what is known as a "callback" to your
client. A callback occurs when you ask the OPC server to notify your client only
when data changes.
Launch:
These permissions are what allow an OPC client application to start or "launch"
an EXE running on the machine where the OPC server is located.
There are two common EXEs that get launched:
OPCEnum.exe, a standard OPC common component that lists the available
OPC servers on a machine and returns that list to a client;
The actual EXE that corresponds to the OPC server.
Configuration:
These permissions allow a remote client to change the configuration of the OPC
server set-up in the registry - you should rarely have to touch these permis-
sions. In fact, you should not do so unless you are an expert with DCOM, and
have a specific reason for doing so.
The underlying objective here is to allow wide access to the general applica-
tions installed on the client and server PCs, while restricting access to the OPC
server.
To ensure that the OPC server and clients will be able to communicate correctly,
modify the following settings after MK8000 installation.
To do this, in Windows XP computers, perform the following steps:
1) Log in as Administrator (necessary for modifying DCOM privileges).
2) Open the DCOM settings window (\WINNT\System32\dcomcnfg.exe).
3) In the Component Service window, right-click the node:
Component Services
Computers
My Computer
4) In the menu that appears, select ‘Properties’
The Computer Properties window will appear (Fig. 73).
