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Reading OPC DA Items Cyclic

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07 Mar 2022 11:15 #10707 by support
Replied by support on topic Reading OPC DA Items Cyclic
Hello.

QuickOPC does connection/disconnections for you, you cannot directly control it ( opclabs.doc-that.com/files/onlinedocs/QuickOpc/Latest/User%2...tml#Connection%20handling.html )

QuickOPC holds the connection open for some time after each read. If your code makes the next reader after a longer time, a new connection will be needed. You can increase the hold period for it to be longer than your read cycles, and then the connection will stay open.

An example of setting the hold period is here:
- opclabs.doc-that.com/files/onlinedocs/QuickOpc/Latest/User%2...tting%20a%20hold%20period.html

But it does the opposite (setting it very short). You need to set it longer (and for Read, not for Write, so it would be the .TopicRead property)

Best regards

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07 Mar 2022 10:36 #10706 by mut9bu
Hello
I can connect to the remote OPC server and read multiple tags with the following code, without problem. But I want to read the items periodicaly.
If I run the code periodicaly, i think i will also make the connection to the OPC DA Server each time repeatedly.
How can I first just make the connection to the OPC DA server, and then read the items? (seperately)
So , i could run just the reading part periodically.
I couldnt a find a code example, for just connecting to the server (without reading tag)

Or is there a better way for reading periodically?


public static void Main1()
{
// Instantiate the client object.
var client = new EasyDAClient();

DAVtqResult[] vtqResults = client.ReadMultipleItems("opcda://10.92.XXX.XXX/OPC.IwSCP.1",
new DAItemDescriptor[]
{
"Simulation.Random", "Trends.Ramp (1 min)", "Trends.Sine (1 min)", "Simulation.Register_I4"
});

for (int i = 0; i < vtqResults.Length; i++)
{
Debug.Assert(vtqResults != null);

if (vtqResults.Succeeded)
Console.WriteLine("vtqResults[{0}].Vtq: {1}", i, vtqResults.Vtq);
else
Console.WriteLine("vtqResults[{0}] *** Failure: {1}", i, vtqResults.ErrorMessageBrief);
}
}

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