CODEWITHSUNDEEP
opcopc-da
Jared Beach
Jared Beach

Reputation: 3163

Close OPC DA Connections

I am using OPC Foundation's OpcNetApi.dll to communicate with an OPC DA server.

I am curious if there is a programatic way to kill specific connections which are currently active on the server using this library or a similar library.

Upvotes: 1

Views: 982

Answers (1)

bruceceng
bruceceng

Reputation: 2182

I'm not positive, but I don't think what you are asking for is always possible (without a debugger). OPC is based on Microsoft COM. There are two ways that COM can be implemented:in-proc and out-of-proc. The choice depends on the OPC server vendor.

With an in-proc implementation, if you are running the OPC client on the same machine as the OPC server then the OPC server is just a dll that is loaded directly into the memory space of the OPC client. This dll exposes the OPC interfaces like CreateGroup, ReadAllItems, etc. Now it is probably getting the actual data through some other mechanism (named pipe, TCP/IP, etc) but this depends again on the OPC server implementation. The only way to really force stop this OPC server is to end the OPC client or get the OPC client program. Of course the OPC client or OPC server may already have implemented a mechanism to end, but there is not guarantee.

If it is an out-of-proc OPC implementation then the OPC server will run in a separate executable so you can find the name of that executable and terminate it. (You can search in regedit for the name of the OPC server to find the corresponding executable name). If I remember correctly, the OPC server can be designed so all clients share one executable or each OPC client gets their own instance of the executable.

If you are running the OPC server remotely then it is probably going to be loaded inside of a stub program if its an in-proc implementation and then tied to RPC. If you block the ports that RPC communicates over I think most clients would decide to disconnect after a while, although there is no guarentee they won't try to reconnect later.

Here's some more information: https://www.opcsupport.com/link/portal/4164/4590/Article/711/May-I-get-a-In-Proc-and-Out-Of-Proc-explanation

Upvotes: 0

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