Hi Tomasz,

I'm trying to write a subscription service similar to this chat service.  Below is my web.config:

<?xml version="1.0"?>
<configuration>

<system.web>
<compilation debug="true" targetFramework="4.0" />
</system.web>
<system.serviceModel>
<extensions>
<bindingElementExtensions>
<add name="pollingDuplex" type="System.ServiceModel.Configuration.PollingDuplexHttpBindingElement, System.ServiceModel.PollingDuplex, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"/>
</bindingElementExtensions>
</extensions>
<bindings>
<customBinding>
<binding name="MAD.ChangeNotificationServices.SubscriptionService.customBinding0">
<binaryMessageEncoding />
<pollingDuplex duplexMode="MultipleMessagesPerPoll"></pollingDuplex>
<httpTransport />
</binding>
</customBinding>
</bindings>
<services>
<service name="MAD.ChangeNotificationServices.SubscriptionService">
<endpoint address="" binding="customBinding" bindingConfiguration="MAD.ChangeNotificationServices.SubscriptionService.customBinding0"
contract="MAD.ChangeNotificationServices.ISubscriptionService" />
<endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange" />
</service>
</services>
<behaviors>
<serviceBehaviors>
<behavior>
<!-- To avoid disclosing metadata information, set the value below to false and remove the metadata endpoint above before deployment -->
<serviceMetadata httpGetEnabled="true"/>
<!-- To receive exception details in faults for debugging purposes, set the value below to true. Set to false before deployment to avoid disclosing exception information -->
<serviceDebug includeExceptionDetailInFaults="false"/>
<serviceThrottling maxConcurrentSessions="2147483647"/>
</behavior>
</serviceBehaviors>
</behaviors>
<serviceHostingEnvironment aspNetCompatibilityEnabled="true"
multipleSiteBindingsEnabled="true" />
</system.serviceModel>
<system.webServer>
<modules runAllManagedModulesForAllRequests="true"/>
</system.webServer>

</configuration>

When I use SingleMessagePerPoll as my duplex mode, everything works fine.  But when I switch to MultipleMessagesPerPoll, calls to the subscription service result in an operation timeout after 1 minute.  If I place a break point in the method I am calling in the subscription service, the break point is never hit.  Do you have any wisdom to share?