Identifying OPC servers: do I need opc.exe? Where is it?

[bwllc]

Hi there,

I've been reading OPC documentation for a few days. I hope that I'm familiar enough with OPC to ask the right questions.

I have a Python application to which I want to add OPC client capabilities, so I'm trying to use OpenOPC. In order for a client to connect, it has to have an OPC server name.

I have an OPC Server running in Rockwell RSLinx Classic. The RSLinx Classic package includes an OPC Test Client. The Client program produces a list of OPC Servers to which I can connect (there are a few extra servers on my machine from National Instruments, I'm not sure how they got there). I choose a server and connect.

Now I want to write my own client. How can I get the OPC Server list in OpenOPC? According to the README.TXT, I'm supposed to:

1. Get a listing of the available OPC servers on your computer by
   going to the command prompt and entering:

opc -q

2. Set your prefered OPC server as the default by setting the system
   wide enviornment variable OPC_SERVER. (On Windows you can do this
   by going to Control Panel > System > Advanced > Environment Variables)

I have looked high and low in this software package, and on my computer, for a program called opc.exe. I cannot find it.

I have discovered that I have an executable service program called OpcEnum.exe. It's not on the system path, but it's apparently accessible as a Windows system service. My Services tab shows that it is running. Presumably Rockwell obtains OPC server names from this service. If you run OpcEnum.exe at the command line, it returns no information to the console.

Any help you can provide in understanding how to identify available OPC servers would be greatly appreciated. Thanks!