# Reading OPC tag from another gateway without subscribing tag

**URL:** <https://forum.inductiveautomation.com/t/reading-opc-tag-from-another-gateway-without-subscribing-tag/16295>\
**Category:** Ignition\
**Created:** [December 12, 2017, 12:29am UTC](https://forum.inductiveautomation.com/t/reading-opc-tag-from-another-gateway-without-subscribing-tag/16295 "2017-12-12T00:29:39Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![wng](https://avatars.discourse-cdn.com/v4/letter/w/f14d63/32.png) [@wng](https://forum.inductiveautomation.com/u/wng)\
**Post date:** [December 12, 2017, 12:29am UTC](https://forum.inductiveautomation.com/t/reading-opc-tag-from-another-gateway-without-subscribing-tag/16295/1 "2017-12-12T00:29:39Z")

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Hi,

I am trying to use the system.opc.readValue function to read a tag value from an OPC server that is in a different gateway than the designer project gateway.

The tag browser can read the value with no issues, but when I use the opc.readvalue function with the same itempath/opcserver format I get a null value with this status:  
[Bad\_NodeIdUnknown] The node id refers to a node that does not exist in the server address space

Is there a way to read the OPC tag value from a different gateway without subscribing the tag into the tag browser?

Thanks in advance!

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**Author:** ![gkawaguchi](https://avatars.discourse-cdn.com/v4/letter/g/919ad9/32.png) [@gkawaguchi](https://forum.inductiveautomation.com/u/gkawaguchi)\
**Post date:** [December 12, 2017, 4:32pm UTC](https://forum.inductiveautomation.com/t/reading-opc-tag-from-another-gateway-without-subscribing-tag/16295/2 "2017-12-12T16:32:54Z")

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I’m guessing there’s a syntax problem involved. I do that all the time and it works. You don’t have to subscribe, opc.readValue is all you need for a one time read operation.