One added footnote, when I use easyopc or poweropc, the results are the same. One thing to note, I tried both opc clients with another identical opc server on the network called "scada-2", what is interesting is when attemping to communicate to SCADA-2, I get "Access denied" with both opc clients. I checked, all services are running on SCADA-2 and the firewall is off.

Just thought it might help.

Hello,

The other OPC client I was using is called poweropc. It does the same thing easyopc cleint does. See screen shot. What is interesting about the other software, is that it cannot find the OPC servers on the "SCADA" computer either.

David

Hello,

I am sorry for the confusion. I may have also given you some slightly wrong information. I re-checked everything and came up with 2 screen shots that should help you to see whats going on.

So to review. I have 2 computers. One, Called "SCADA", which has several working OPC servers on it, and the other computer called "Develop" on the same Local area network as "SCADA". On "SCADA" I am interested in accessing data from either OPC server named "Citect.OPC.1" or "Citect.OPCRemote.1". Either one will work. And both work locally for data reads and writes.

When I use your OPC demo application locally on "SCADA": I can browse for OPC servers, and connect to both "Citect.OPC.1" or "Citect.OPCRemote.1" and reads and writes data to tags. Please See screen shots attached.

When I use your OPC demo application over the LAN from "Develop" to "SCADA": I can browse for machines and it does find them. However, I cannot browse for OPC Servers on remote machines. When I do attempt to look for OPC Servers on "SCADA", I get the "RPC server not available message". Also if I manually type in the Machine Name "SCADA", and manually enter the OPC server name, I cannot read nor write data to either "Citect.OPC.1" or "Citect.OPCRemote.1" . The response I get, after manually entering the machine "SCADA" and server name "Citect.OPCRemote.1" is "The RPC Server is not available". The response I get, after manually entering the machine "SCADA" and server name "Citect.OPC.1" is that long failure string. Please See screen shots attached for specific error messages.

All DCOM and RPC services are running on both computers, and it makes no difference if the firewall is on or off.

This has all been verified to be true and correct as I have explained it here. Please Forgive me, I should have been more careful with my description of events before. As such I have tried to be very specific in this case to avoid any more confusion.

Thank you for your help!

David Perotti

Hello,

Ok I did some more testing, To verify everything is ok. I went to the server computer. On the server OPCEnum is running. Also I ran your OPC client demo and looked at an active tag locally on the server computer. Everything was fine, tag read successfully via OPC...

So I went back to the remote computer. Manually entered the machine name, OPCServer name, and a the same tag name I was reading locally on the server computer. On the remote computer I got the "RPC server unavailable" error message this time.

The reason I got the other error last time is because I made a typo. I have attached a screen shot from the remote computer side. Is there any thing else I could be missing?

David P

Hello,

Sorry it took so long to get an update. As of Right now, simply using your demo OPC client, trying to browse for OPC servers on a remote computer I get the "RPC server unavailable" message. If I enter the server name manually, then browse for tags, same thing happens. If I enter all the correct information, then try to read or write the tag I get:

"Server failed. This error originates in the OPC Data Access server. A vendor specific fatal error has occurred within the server. The server is no longer functioning. The recovery procedure from this situation is vendor specific. The application will try to reconnect to the server after a configurable period. Technical information: The call to IOPCServer::GetStatus on the OPCServer object has returned OPC_STATUS_FAILED in the OPCSERVERSTATUS structure. "

I also tried using another company's OPC client and get same results. Turning the firewall on or off makes no difference, and all the associated Services are running of the computer in question.

PLEASE HELP!