# Problem with S7400 Driver

**URL:** <https://forum.inductiveautomation.com/t/problem-with-s7400-driver/10615>\
**Category:** General Discussion\
**Created:** [October 13, 2015, 7:10pm UTC](https://forum.inductiveautomation.com/t/problem-with-s7400-driver/10615 "2015-10-13T19:10:16Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![maripierdo](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/maripierdo/32/16478_2.png) [@maripierdo](https://forum.inductiveautomation.com/u/maripierdo)\
**Post date:** [October 13, 2015, 7:10pm UTC](https://forum.inductiveautomation.com/t/problem-with-s7400-driver/10615/1 "2015-10-13T19:10:16Z")

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I´m watching this error in my console. Could you help me?

S7400Driver[PLC\_01] Error getting request key.   
com.inductiveautomation.xopc.drivers.siemens.util.ReadException: Error reading field “Header Constant” at offset 7 in bytes: [03 00 00 07 02 F0 00]  
at com.inductiveautomation.xopc.drivers.siemens.structs.readers.AbstractStructReader.read(AbstractStructReader.java:25)  
at com.inductiveautomation.xopc.drivers.siemens.structs.readers.AbstractStructReader.read(AbstractStructReader.java:14)  
at com.inductiveautomation.xopc.drivers.siemens.S7Driver.readKeyFromS7Message(S7Driver.java:361)  
at com.inductiveautomation.xopc.drivers.siemens.S7Driver.getRequestKey(S7Driver.java:334)  
at com.inductiveautomation.xopc.drivers.siemens.S7Driver.getRequestKey(S7Driver.java:68)  
at com.inductiveautomation.xopc.driver.api.AbstractDriver.messageArrived(AbstractDriver.java:699)  
at com.inductiveautomation.xopc.driver.api.AbstractSocketDriver.messageArrived(AbstractSocketDriver.java:194)  
at com.inductiveautomation.xopc.driver.api.AbstractSocketDriver$DriverIOEventHandler$1.run(AbstractSocketDriver.java:257)  
at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)  
at java.util.concurrent.FutureTask.run(Unknown Source)  
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(Unknown Source)  
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(Unknown Source)  
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)  
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)  
at java.lang.Thread.run(Unknown Source)  
Caused by: java.nio.BufferUnderflowException  
at java.nio.Buffer.nextGetIndex(Unknown Source)  
at java.nio.HeapByteBuffer.get(Unknown Source)  
at com.inductiveautomation.xopc.drivers.siemens.structs.readers.S7HeaderReader.readFields(S7HeaderReader.java:20)  
at com.inductiveautomation.xopc.drivers.siemens.structs.readers.S7HeaderReader.readFields(S7HeaderReader.java:7)  
at com.inductiveautomation.xopc.drivers.siemens.structs.readers.AbstractStructReader.read(AbstractStructReader.java:23)

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<div class="post-metadata">

**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\
**Post date:** [October 13, 2015, 7:13pm UTC](https://forum.inductiveautomation.com/t/problem-with-s7400-driver/10615/2 "2015-10-13T19:13:01Z")

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It looks like this may be the same issue as here: [inductiveautomation.com/forum/v … 72&t=14528](https://inductiveautomation.com/forum/viewtopic.php?f=72&t=14528)

Can you get a Wireshark capture to confirm?