Installation Issues

It is assumed that the server vendor will provide a SETUP.EXE to install the needed components for their server. This will not be discussed further. Other than the actual components, the main issue affecting OLE software is management of the Windows Registry and Component Catagories. The issues here are (a) what entries need to be made and (b) how they can be made.

Again, certain common installation and registry topics including self registration, automatic proxy/stub registration and registry reference counting are discussed in the OPC Overview Document

Component Categories The OPC Data Access Interface defines the following Component Catagories. Listed below are the CATIDs, Descriptors and Symbolic Equates to be used for Data Access.

"OPC Data Access Servers Version 1.0"

CATID_OPCDAServer10 = {63D5F430-CFE4-11d1-B2C8-0060083BA1FB}

"OPC Data Access Servers Version 2.0"

CATID_OPCDAServer20 = {63D5F432-CFE4-11d1-B2C8-0060083BA1FB}

It is expected that a server will first create any category it uses and then will register for that category. Unregistering a server should cause it to be removed from that category. See the ICatRegister documentation for additional information.

 Registry Entries for Custom Interface The following entries are the minimum required to support the Custom Interface for OPC Compliant Servers.

Required by all:

1. HKEY_CLASSES_ROOT\Vendor.Drivername.Version = A Description of your server

2. HKEY_CLASSES_ROOT\Vendor.Drivername.Version\CLSID = {Your Server’s unique CLSID}

3. HKEY_CLASSES_ROOT\Vendor.Drivername.Version\OPC

4. HKEY_CLASSES_ROOT\Vendor.Drivername.Version\OPC\Vendor =Your vendor name

5. HKEY_CLASSES_ROOT\CLSID\{Your Server’s unique CLSID} = A Description of your server

6. HKEY_CLASSES_ROOT\CLSID\{Your Server’s unique CLSID}\ProgID = Vendor.Drivername.Version

One or more of the following lines (inproc and/or local/remote and/or handler)

7. HKEY_CLASSES_ROOT\CLSID\{Your Server’s unique CLSID}\InprocServer32 = Full Path to DLL

8. HKEY_CLASSES_ROOT\CLSID\{YourServer’s unique CLSID}\LocalServer32 = Full Path to EXE

9. HKEY_CLASSES_ROOT\CLSID\{YourServer’s unique CLSID}\InprocHandler32 = Full Path to DLL
  1. This entry simply establishes your ProgID as a subkey of the ROOT under which other subkeys can be entered. The description (the ‘value’ of this key) may be presented to the user as the name of an available OPC server (See example below). It should match the description in line 6.
  2. The CLSID line enables the CLSIDFromProgID function to work. I.e. allows the system to open a key given the ProgID and obtain the CLSID as the value of that key. See the example below.
  3. The OPC line creates a ‘flag’ subkey that has no value. This was used for Data Access 1.0 to allow the client to browse for the available OPC servers. As of verson 2.0, the prefered approach is for clients and servers to use Component Catagories.
  4. The Vendor line is optional. It is simply a means of identifying the vendor who supplied the particular OPC server.
  5. This line simply establishes your CLSID as a subkey off of ROOT\CLSID under which the other subkeys can be entered. The description (the ‘value’ of this key) should be a User Friendly description of the server. It should match Item 1 above.
  6. The ProgID line enables the ProgIDFromCLSID function to work. I.e. allows the system to open a key given the CLSID and obtain the ProgID as the value of that key. (This function is not commonly used).
  7. The InprocServer32 line or LocalServer32 line or InprocHandler32 line allows CoCreateInstance to locate the DLL or EXE given the CLSID. The vendor should define at least one of these.
In general, self registration as described in the Microsoft documentation is recommended for both DLL and EXE servers to simplify installation. Registry Entries for the Proxy/Stub DLL The proxy/stub DLL is used for marshalling interfaces to LOCAL or REMOTE servers. It is generated directly from the IDL code and should be the same for every OPC Server. In general the Proxy/Stub will use self registration. (Define REGISTER_PROXY_DLL during the build). Since this is completely automatic and transparent it is not discussed further.

Also note that a prebuilt and tested proxy/stub DLL will be provided at the OPC Foundation Web site making it unnecessary for vendors to rebuild this DLL.

Although vendors are allowed to add their own interfaces to OPC objects (as with any COM object) they should NEVER modify the standard OPC IDL files or Proxy/Stub DLLs to include such interfaces. Such interfaces should ALWAYS be defined in a separate vendor specific IDL file and should be marshalled by a separate vendor specific Proxy/Stub DLL.