OPC DA client
Purpose
OPC DA Client connects to a Windows OPC DA server, browses ItemNames, reads and writes test items, imports variables, and maintains subscriptions.
Open the plugin
Enter "Development Configuration → Collection Configuration", create a device and select "OPC DA Client" in "Collection Plugin".
Supported channels and data types
| Channel type | Pre-configuration check |
|---|---|
| Plugin built-in connection | Connection parameters are configured in device properties and do not use public TCP, UDP, or serial fields. The plugin is Windows-only. |
Optional data type: The OPC DA Item's actual Canonical Type. Read a node in the debug page first, then choose the matching Boolean, integer, floating-point, or String type.
Plugin properties
The following fields are OPC DA-specific. Configure common retry and write-priority fields through Collection Configuration.
Connection configuration
| Setting | Description |
|---|---|
| OPC server IP | Default: localhost; fill in: text input. Set the OPC server IP used when establishing a connection. |
| OPC server name | Default: Kepware.KEPServerEX.V6; fill in: text input. Set the OPC server name used when establishing a connection. |
Data format
| Setting | Description |
|---|---|
| Server time | Default: Yes; fill in: switch. When enabled, the variable collection time uses the OPC DA Source Timestamp; when disabled, it uses the gateway receive time. |
Subscription configuration
| Setting | Description |
|---|---|
| Subscription mode | Default: Yes; fill in: switch. When enabled, OPC DA DataChanged events push values; when disabled, the gateway polls at the subscription update rate. |
Running parameters
| Setting | Description |
|---|---|
| Detection reconnection frequency (min) | Default: 10; fill in: number input. Reconnection checks run in minutes after a disconnect. |
| Subscription update frequency | Default: 1000; fill in: number input. Requested OPC DA subscription update period in milliseconds. |
Variable configuration
| Setting | Description |
|---|---|
| Dead zone | Default: 0; fill in: number input. Passed to the OPC DA subscription group; units and limits are defined by the OPC DA server. 0 disables the deadband. |
Request packing
| Setting | Description |
|---|---|
| Maximum group size | Default: 500; fill in: number input. Maximum Items in one OPC DA subscription group; larger sets are split into multiple groups. |
Address rules
- ItemName
Functions
| Function | Purpose |
|---|---|
| Browse nodes | Browse the OPC DA address space and inspect ItemName, value, quality, and timestamp. |
| Read and write nodes | Read one selected item; writing changes the server value and requires an approved test item. |
| Export and import | Export selected nodes to a variable file or import them into the current device. |
| Subscription management | Create, inspect, or cancel subscription groups for selected items. |
Device debug
Enter "Development Configuration → Collection Configuration", select the current device and click "More Functions", then open "Debug".
Protocol Debugging · OpcDa
Browse an ItemName and read its value before creating a subscription or importing variables. Use writes only for an approved server test item.
Debugging notes
Browse the OPC DA node and read the values before establishing a subscription; review the address and data type after importing the variables.
Verify the configuration
- Browse to a known ItemName and read the current value. Confirm that the quality is good.
- Change the approved test item on the server and confirm that a read or subscription update appears.
- Import a small set of test nodes and check ItemName, data type, value, and timestamp.
- When subscription mode is enabled, keep the group within Maximum group size and confirm the update rate and deadband.
- Write only to a server-approved test item, then read it again.
Troubleshooting
- The server cannot be browsed: Confirm that GatewayRuntime runs on Windows and check OPC server IP, ProgID, DCOM permissions, and the server process.
- Browsing works but quality is bad: Check ItemName, the server-side device connection, and item quality rather than only the numeric value.
- Subscription does not update: Check Subscription mode, update frequency, deadband, and group size.
- Imported variables have no value: Confirm the ItemName matches the server and check the variable data type and device log.
- Remote OPC DA connection fails: Check DCOM identity, permissions, and Windows firewall rules on both hosts.
Related links
- Collection configuration: View channel, device and common variable configuration.
- Plugin Index: Find other collection or data-forward plugins.