View source for Using OpcCmd Utility as OPC DA Client

[[Category:OPC DA]] [[Category:OpcCmd Utility]] [[Category:Tools and Online Services]] 
For general information about the OpcCmd tool, see [[:Category:OpcCmd Utility]].

= Quickstarts =
== Read item value ==
<pre>OpcCmd> daClient readItem OPCLabs.KitServer.2 Demo.Ramp --value

Reading item value...
Result (value): 6.63516521453857
</pre>
== Browse nodes ==
<pre>OpcCmd> daClient browseNodes OPCLabs.KitServer.2 Simulation --elementNameFilter Incrementing*

Browsing nodes...
Result (sequence): OPC DA node elements: [5] {Incrementing (10 s) -> Simulation.Incrementing (10 s), ...}
╒══╤═════════════════════╤════════════════════════════════╤═════════╤════╤════╤══════╤═════╕
│[]│Name                 │Item ID                         │Node Path│Is  │Is  │Is    │Is   │
│  │                     │                                │         │Leaf│Item│Branch│Hint │
╞══╪═════════════════════╪════════════════════════════════╪═════════╪════╪════╪══════╪═════╡
│ 0│Incrementing (10 s)  │Simulation.Incrementing (10 s)  │         │True│True│True  │False│
│ 1│Incrementing (1 s)   │Simulation.Incrementing (1 s)   │         │True│True│False │False│
│ 2│Incrementing (1 min) │Simulation.Incrementing (1 min) │         │True│True│True  │False│
│ 3│Incrementing         │Simulation.Incrementing         │         │True│True│True  │False│
│ 4│Incrementing (10 min)│Simulation.Incrementing (10 min)│         │True│True│True  │False│
╘══╧═════════════════════╧════════════════════════════════╧═════════╧════╧════╧══════╧═════╛</pre>

= Commands, Arguments and Options =

== Command: daClient subscribeItem ==

<pre>
OpcCmd -i
daClient
subscribeItem OPCLabs.KitServer.2 Demo.Ramp 200
</pre>

= Tips and Tricks =
== Using OPC NET API implementation ==
If you want to use the OPC NET API implementation  instead of the native implementation (in OpcCmd for .NET Framework), you can do it interactively as in the following example:
<pre>
OpcCmd -i
daClient --property InstanceParameters.EnableNativeClient=[Boolean]false
subscribeItem OPCLabs.KitServer.2 Demo.Ramp 200
</pre>
If you want to use such setting permanently, you can modify one of the OpcCmd [[Intrinsic Component Configuration]] files (JSON, INI or XML). For example, with the JSON format, put the following into the '''appsettings.json''' or '''appsettings.production.json''' file:
<syntaxhighlight lang="json">
{
  "OpcLabs.EasyOpc.DataAccess.EasyDAClient": {
    "InstanceParameters": {
      "EnableNativeClient": false
    }
  } 
}
</syntaxhighlight>
Note that in .NET Core and .NET 5.0+, OPC NET API is the only available implementation and is thus selected by default.

== OPC DA Optimizer settings ==
Turn off request chunking: <code>plugins configuration part DAOptimizerPluginParameters set EnableRequestChunking [Boolean]False</code>

Turn off request merging: <code>plugins configuration part DAOptimizerPluginParameters set EnableRequestMerging [Boolean]False</code>

Turn off subscription blending: <code>plugins configuration part DAOptimizerPluginParameters set EnableSubscriptionBlending [Boolean]False</code>
== Volume Testing ==
In order to read or subscribe to the same item many times, use the '''multiple''' sub-command with the '''--repeat''' option. You will probably need to combine this with turning off the request merging and/or subscription blending, and consider turning off request chunking.

Example 1: <code>readItem http://opcxml.demo-this.com/XmlDaSampleServer/Service.asmx "Dynamic/Analog Types/Double" multiple --repeat 2000</code>

Example 2: <code>subscribeItem http://opcxml.demo-this.com/XmlDaSampleServer/Service.asmx "Dynamic/Analog Types/Double" multiple --repeat 2000</code>