More canonical test.
There is an exception happening around here in some cases when connection is dropped while waiting for answer. Not sure that this fixes it but this is anyhow better.
<?xml version='1.0' encoding='utf-8'?>
<project xmlns:ns1="http://www.plcopen.org/xml/tc6_0201" xmlns:xhtml="http://www.w3.org/1999/xhtml" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns="http://www.plcopen.org/xml/tc6_0201">
<fileHeader companyName="Beremiz" productName="Beremiz" productVersion="1" creationDateTime="2015-02-05T11:44:55" contentDescription=" "/>
<contentHeader name="WAMPTest" modificationDateTime="2015-02-18T23:59:50">
<coordinateInfo>
<fbd>
<scaling x="0" y="0"/>
</fbd>
<ld>
<scaling x="0" y="0"/>
</ld>
<sfc>
<scaling x="0" y="0"/>
</sfc>
</coordinateInfo>
</contentHeader>
<types>
<dataTypes/>
<pous>
<pou name="program0" pouType="program">
<interface>
<localVars>
<variable name="LocalVar0">
<type>
<DINT/>
</type>
</variable>
</localVars>
<externalVars>
<variable name="PyVar0">
<type>
<DINT/>
</type>
</variable>
<variable name="PyVar1">
<type>
<DINT/>
</type>
</variable>
</externalVars>
</interface>
<body>
<FBD>
<inVariable localId="1" executionOrderId="0" height="25" width="55" negated="false">
<position x="144" y="70"/>
<connectionPointOut>
<relPosition x="55" y="12"/>
</connectionPointOut>
<expression>PyVar0</expression>
</inVariable>
<block localId="3" typeName="ADD" executionOrderId="0" height="60" width="65">
<position x="245" y="52"/>
<inputVariables>
<variable formalParameter="IN1">
<connectionPointIn>
<relPosition x="0" y="30"/>
<connection refLocalId="1">
<position x="245" y="82"/>
<position x="199" y="82"/>
</connection>
</connectionPointIn>
</variable>
<variable formalParameter="IN2">
<connectionPointIn>
<relPosition x="0" y="50"/>
<connection refLocalId="4">
<position x="245" y="102"/>
<position x="228" y="102"/>
<position x="228" y="113"/>
<position x="198" y="113"/>
</connection>
</connectionPointIn>
</variable>
</inputVariables>
<inOutVariables/>
<outputVariables>
<variable formalParameter="OUT">
<connectionPointOut>
<relPosition x="65" y="30"/>
</connectionPointOut>
</variable>
</outputVariables>
</block>
<inVariable localId="4" executionOrderId="0" height="25" width="73" negated="false">
<position x="125" y="101"/>
<connectionPointOut>
<relPosition x="73" y="12"/>
</connectionPointOut>
<expression>LocalVar0</expression>
</inVariable>
<outVariable localId="2" executionOrderId="0" height="25" width="55" negated="false">
<position x="344" y="70"/>
<connectionPointIn>
<relPosition x="0" y="12"/>
<connection refLocalId="3" formalParameter="OUT">
<position x="344" y="82"/>
<position x="310" y="82"/>
</connection>
</connectionPointIn>
<expression>PyVar1</expression>
</outVariable>
</FBD>
</body>
</pou>
</pous>
</types>
<instances>
<configurations>
<configuration name="config">
<resource name="resource1">
<task name="Task0" priority="0" interval="T#100ms">
<pouInstance name="Instance0" typeName="program0"/>
</task>
</resource>
</configuration>
</configurations>
</instances>
</project>