I've cimplicity HMI act as a OPC server on WinNT. My client tell me that he has a OPC client on unix(!). Can they receive my point values over the TCP-IP network. Is interoperability supported between windows OPC and Unix OPC.
DCOM is nothing that special. Other people have ported DCOM over to other platforms, and with a little work you can get not only an OPC client but also an OPC server running on other operating systems. You can go to the OpenGroup's web site (http://www.opengroup.org) and either get the reference documentation on COM/DCOM or you can get there implementation of it. I think the developer's license is around 8K, go to http://www.opengroup.org/comsource.
OPC uses DCOM for client-server communications if the client and server reside on seperate machines, and COM if they are on the same
machine. Having a unix OPC client would require COM/DCOM on unix -- a non-trivial task, the only implementations that I know of are in the
millions of dollars and I think they are COM only, no DCOM. There may have been a missunderstanding somewhere along the line.