# Designer-Gateway Comm via RPC

**URL:** <https://forum.inductiveautomation.com/t/designer-gateway-comm-via-rpc/3207>\
**Category:** Module Development\
**Created:** [August 22, 2011, 4:21pm UTC](https://forum.inductiveautomation.com/t/designer-gateway-comm-via-rpc/3207 "2011-08-22T16:21:12Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![jmino](https://avatars.discourse-cdn.com/v4/letter/j/3d9bf3/32.png) [@jmino](https://forum.inductiveautomation.com/u/jmino)\
**Post date:** [August 22, 2011, 4:21pm UTC](https://forum.inductiveautomation.com/t/designer-gateway-comm-via-rpc/3207/1 "2011-08-22T16:21:12Z")

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Hi,

I’ve created a simple example, almost identical to the Design Best Practice in Section 4.6 of the programming guide (p.47). I’ve added a toolbar button that invokes a method, but an error is thrown:

`com.inductiveautomation.ignition.client.gateway_interface.GatewayException: Gateway Error 500: Unable to read response from Gateway.
	at com.inductiveautomation.ignition.client.gateway_interface.GatewayInterface.newGatewayException(GatewayInterface.java:280)
	at com.inductiveautomation.ignition.client.gateway_interface.GatewayInterface.getResponse(GatewayInterface.java:348)
	at com.inductiveautomation.ignition.client.gateway_interface.GatewayInterface.sendMessage(GatewayInterface.java:219)
	at com.inductiveautomation.ignition.client.gateway_interface.GatewayInterface.sendMessage(GatewayInterface.java:214)
	at com.inductiveautomation.ignition.client.gateway_interface.GatewayInterface.moduleInvoke(GatewayInterface.java:640)
	at org.test.pkg.designer.TestModuleRPCProxy.invoke(TestModuleRPCProxy.java:15)
..
.
Caused by: org.xml.sax.SAXParseException: The end-tag for element type "Response" must end with a '>' delimiter.
	at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(Unknown Source)
..
.
`  
The getRPCHandler method is called in the GatewayHook, but I haven’t been able to determine what is happening beyond that.

Is this something that has been encountered before? Any advice on where I might be going wrong?

Thanks,  
-JM

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<div class="post-metadata">

**Author:** ![jmino](https://avatars.discourse-cdn.com/v4/letter/j/3d9bf3/32.png) [@jmino](https://forum.inductiveautomation.com/u/jmino)\
**Post date:** [August 23, 2011, 12:29pm UTC](https://forum.inductiveautomation.com/t/designer-gateway-comm-via-rpc/3207/2 "2011-08-23T12:29:55Z")

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Update on this one:  
The error was a bit cryptic. The problem was in my build file. I mistakenly packed the jar file of the common project before adding it to the module, so a NoClassDefFoundError occurred when I invoked the RPC method, and didn’t show up in the logs.  
Problem solved.