Reading and Writing Shared Variables with the Variable Web Service

LabVIEW 2018 Help


Edition Date: March 2018
Part Number: 371361R-01
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Using the variable Web service, you can create applications that access network-published shared variables through HTTP. Any shared variables that utilize the NI Publish-Subscribe Protocol (NI-PSP) can be accessed using the variable Web service. Using Open Data Protocol (OData), the variable Web service provides responses in both XML and JSON formats.

Note  The variable Web service does not support the following OData parameters: $filter, $select, $top, $skip, $links, $orderby, $inlinecount, and $batch.

Installing the Variable Web Service on a Real-Time Target

To use the variable Web service on an RT target, install Variable Web Service 12.0.0 on the RT target using the LabVIEW Real-Time Software Wizard in NI Measurement & Automation Explorer (MAX).

Granting New Permissions to Users

To use the variable Web service, you must grant the appropriate permissions to the appropriate users in NI Web-based Configuration & Monitoring. The following permissions are included with the variable Web service:

  • VariableBrowse
  • VariableRead
  • VariableWrite
  • VariableCreateDeleteGroup
  • VariableReadGroup

By default, these permissions are granted to the admin only. For information about granting permissions to users, launch NI Web-based Configuration & Monitoring and click Help on the Web Server Configuration page.

To identify themselves and utilize these permissions, users must log in to NI-Auth when prompted. Alternatively, the admin can disable authentication by granting all five permissions to the everyone group.

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