Principle of remote access to OPC-DA server by means of DCOM
2) However in case of the
OPC server, there is another recommended, easier and better procedure. In such case the
OPC server is installed only on the server side. On the client side, it is necessary to install
OPC core components redistributable package (directly from the
OPC Foundation), allowing the connection to any remote
OPC server. It is even recommended to install such package also on the server (together with the
OPC server) because this package contains the
OPCEnum.exe component (available as
Windows service or as a regular program), that allows the remote clients to list through the installed
OPC servers. The redistributable package can be obtained either from the
www.opcfoundation.org Webpages, or from the MICROSYS company Webpages
https://www.promotic.eu/PmInstall/OPC_CoreComponentsRedistributable.zip. Caution! The package requires installed
.NET version 1.1 and higher (otherwise it cannot be installed). The package contains also the
DCOM access for
.NET applications.
a) If the
OPC core components package is installed also on both client and server sides, then it is possible on the client side in the PROMOTIC system to use button in the "
OPC server - CLSID/ProgID" configurator to browse through the list of installed
OPC servers on the server. The server computer is defined in the "
Run on computer" configurator.
b) If the OPC core components package is installed only on the client side, then it is not possible to browse through the list of installed OPC servers on the server, and it is necessary to enter the CLSID of the remote OPC server manually.
The main condition for connecting to the remote
OPC server (that is not installed locally) is, that the
OPC server link must be defined as
CLSID (e.g.
{00000001-0000-11d1-8011-00A024CFCA34}), not as
ProgID (e.g. "MS.OPCServer.1"). The "
OPC server - CLSID/ProgID" configurator of the
PmaOpcDaClient object, when selected returns
CLSID.
When configuring the
DCOM messages on the server (
DCOMCNFG.EXE) it is necessary to set the corresponding permissions not only for the
OPC server itself, but also for the
OPCEnum program from the redistributable package.
The permissions configuration procedure for
DCOM for both the client and the server side is, for example, available at
http://www.softwaretoolbox.com/dcom/html/dcom_.html.
Configuration of remote access to OPC server by means of DCOM
In order to configure the
DCOM it is necessary to have the
Windows OS administrator rights. The configuration of both
DCOM server and client is similar. On the server, you can also (to
OPCEnum) configure the
OPC server.
1) Server and client: If the computer of the server and the client is not in the domain, then it is necessary to create the user on the server with the same name and password as the user on the client computer (shared user).
2) Server and client: If the simplified file sharing in
Windows OS
XP is swithced on, then the
"Access denied" error occurs when trying to access the remote
OPC server. Therefore it must be turned off.
See
Start > Control Panel > Folder properties > View > Detailed settings > Use simplified file sharing.
3) Server and client:
Launch the console
Start > Programs > Administrative Tools > Local Security Policy.
In the console go to
Local Policies > Security Options
Check the following settings:
- Network access: Let Everyone permissions apply to anonymous users is enabled
- Network access: Sharing and security model for local accounts is set to Classic.
4) Server: Install the
OPC-DA server.
5) Server and client: Install the
OPC core components package (
OPCEnum).
6) Server and client: Launch the
DCOMCNFG.EXE configuration tool (located in
Windows OS subfolder
system32), that represents the
DCOM administration console.
7) Server and client: In the console, go to
Component Services > Computers > My Computer and display the
Properties (by the right mouse button). Here you can manage the configuration of the common parts of
COM,
DCOM and default values for each
COM server.
a) On the
"Default properties" tab, check the settings:
- Enable Distributed COM on this computer is enabled
- Default Authentication Level is set to None
- Default Impersonation Level is set to Identify.
b) On the
"COM Security" tab check the settings:
- In Access Permissions > Edit Limits for Everyone the Local Access and the Remote Access are both enabled
- In Access Permissions > Edit Default for the common user (same for client and server) the Local Access and Remote Access are both enabled
- In Launch and Activation Permissions > Edit Limits for Everyone the Local Launch, Remote Launch, Local Activation and Remote Activation are all enabled
- In Launch and Activation Permissions > Edit Default for the common user (same for client and server) the Local Launch, Remote Launch, Local Activation and Remote Activation are all enabled
8) Server and client: Configuration of
DCOM for the
OPCEnum program from the
OPC core components package.
In the console go to
Component Services > Computers > My Computer > DCOM Config > OPCEnum and display the
Properties (by the right mouse button).
a) On the
"General" tab check if is set
Authentication Level to
None.
b) On the
"Location" tab check if is set
Run application on this computer.
c) On the
"Security" tab check if all options are set to the
Use Default value. The options are
Launch and Activation Permissions,
Access Permissions and
Configuration Permissions.
d) On the
"Identity" tab check the
The system account setting. If another component than
OPCEnum is selected, that is not a service, (e.g.
OPC server), it is also possible to set the login data of specific common user.
9) Server: Configuration of
DCOM for the
OPC-DA server.
In the console go to
Component Services > Computers > My Computer > DCOM Config > OPC server name and display the
Properties (by the right mouse button).
Caution! The configuration of the
OPC server is similar to the
OPCEnum configuration, therefore repeat the steps
8a to
8d.
Caution: Setting of permissions for the PROMOTIC application depends on the location of the PROMOTIC system on the disk.
If the PROMOTIC software is registred or moved to another location, then the
DCOM stops working (the other functions of the PROMOTIC system may continue to work correctly).
If there are multiple PROMOTIC versions on the disk and the user needs to switch between these versions then (from the
DCOM configuration point of view) it is recommended to have the active version of the PROMOTIC system always in the same folder (e.g.
C:\Promotic\PmActive).