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New OPC Connections block existing OPC connections

13 Jan 2015 13:28 #2602 by support
The design goal of the EasyDAClient component is that such blocking should not happen. If it indeed does happen, we will investigate why, and attempt to fix it.

First, however, we should rule out other possible causes. Specifically, since the Tunneler is really just one server, although it presents itself as multiple ones, the blocking can also be caused by the Tunneler.

To find out more, I suggest that enhance your test to include some other server - for example, a local simulation server (OPCLabs.KitServer.2) that we ship with the product, directly (not through the tunneler). When this server becomes the server "A" in your test described below, does an access to a problematic server "B" (through the tunneler) also block the "A"? If it does not, the the tunneler would be to blame for the blocking...

Thank you

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13 Jan 2015 00:06 #2599 by markfiala
Hello, I am using the QuickOPC .net library in a WCF service. I am using the WCF service as a "switchboard" to route OPC item reads and writes to several OPC servers. I am using the library to connect to several OPC servers at once.

I notice a behaviour that when I open a new connection to a new OPC server, it seems to block access for existing connections. For example, if I am connected to OPC server A and reading items smoothly, and then attempt to connect to OPC server B then accesses to OPC server A freeze and wait. A "blocking" behaviour. This is pronounced if OPC server B does not exist (if the server address is wrong or the machine is not available.

I am using it through Matrikon's OPC Tunneler product to connect between my computer and several PC's permanently connected to PLC's through OPC servers running on those PC's. All traffic is going through one instance of my WCF program to all these OPC servers.

I am not a skilled .net programmer but I am pretty sure the WCF service we wrote is set for parallel threads, but it is possible that the problem could be our fault.

Is there any reason inside the QuickOPC library that would account for this? Meaning the whole library has to wait while it attempts to connect to a new OPC server?


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