OPC XML Data Access 1.01 Client communication protocol
Protocol specification
Communication line configuration
Protocol configuration on the communication station
I/O tag configuration
Literature
Changes and modifications
Document revisions
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Protocol specification
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Protocol OPC XML DA is a transitive protokolom between protocols protocol between OPC Data Access Client and OPC Unified Architecture Data Access Client protocols.
An improvement to OPC Data Access Client is is a transition to platform-independent communication (using XML data format and SOAP-Web Services over HTTP protocol).
The latest from the OPC protocol family is the protocol the OPC Unified Architecture Data Access Client which maintains platform independence and optimizes performance by replacing XML/SOAP communications with binary encoding and by eliminating HTTP protocol.
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Communication line configuration
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Communication line category: HTTP client
URL: URL address of OPC XML server in form http://host[:port][/path[?query]], e.g. http://172.16.0.1 or http://myopcserver.domain:8080/opcxml
Proxy: IP address or name of the optional proxy server. If entered, the KOM process will connect to the proxy server instead of the host listed in the URL parameter URL.
User: optional name for the authentication on the proxy server (support for authentication has not been implemented).
Password: optional password for authentication on the proxy server (support for authentication has not been implemented).
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| Parameter | Meaning | Unit | Default value |
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| Debug Responses Parsing | Enable debug messages at the OPC XML server response level. | YES/NO | NO |
| Debug Http I/O Data | Turn on debug messages at the HTTP communication level. | YES/NO | YES |
| Debug Http Responses | Turn on debug messages with headers and the body of HTTP response. | YES/NO | NO |
| Debug Received Values | Turn on debug messages with received values. | YES/NO | YES |
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Protocol configuration on the communication station
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- Communication protocol: OPC XML Data Access 1.01 Client.
- Station address: unused.
Station protocol parameters
Table 1
| Full name | Description | Default value |
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| Request option ReturnErrorText | Parameter of Subscribe and Write requests. If set to YES, the server will return a verbose error description. | NO |
| Request option ReturnDiagnosticInfo | Parameter of Subscribe and Write requests. If set to YES, the server will return verbose server-specific diagnostic information to provide additional information relative to item-specific errors. | NO |
| Request option ReturnItemTime | Parameter of Subscribe and Write requests. If set to YES, the server will return the timestamp for each Item. | YES |
| Request option ReturnItemPath | Parameter of Subscribe and Write requests. If set to YES, the server will return ItemPath (a path to Item within Namespace) for each Item. | NO |
| Request option ReturnItemName | Parameter of Subscribe and Write requests. If set to YES, the server will return ItemName (a fully qualified identifier of Item) for each Item. | NO |
| Request option ReturnValuesOnReply | Parameter of Subscribe and Write requests. If set to YES, the server will return values of all Items in reply to Subscribe and value of Item in reply to Write as if the client had performed a Read request directly after the Write request. | YES |
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I/O tag configuration
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| Name | Meaning |
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| Item Name | Unique text identifier of Data in OPC XML server. |
| Subscribe | If the setting is checked, the KOM process uses this Item in Subscribe request to query the value of the object.
This setting can be unchecked for objects that are not supposed to be read (e.g. write-only I/O tags or objects that have been removed from the communication). |
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