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Editorial Team
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Asked: 2026-05-13T21:25:25+00:00

I have created a web application with a Silverlight project embedded in it, using

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I have created a web application with a Silverlight project embedded in it, using VS 2008 SP 1, and the Silverlight 3 tools, on Vista and Windows 7.

The duplex service code:

    [ServiceContract(Namespace = "cotoco", CallbackContract = typeof(IDuplexClient))]
[ServiceBehavior(InstanceContextMode = InstanceContextMode.Single)]
[AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]
public class DuplexServer
{
private IDuplexClient _client;
private string _message;
private int _messageCounter;

private Timer _timer;

public DuplexServer()
{
}

#region IDuplexServer Members

[OperationContract(IsOneWay = true)]
public void SendEcho(string message)
{
    _client = OperationContext.Current.GetCallbackChannel<IDuplexClient>();
    _message = message;

    _timer = new Timer();
    _timer.Interval = 2000;
    _timer.Enabled = true;
    _timer.Elapsed += new ElapsedEventHandler(_timer_Elapsed);
    _timer.Start();
}

void _timer_Elapsed(object sender, ElapsedEventArgs e)
{
    _client.ReturnEcho(string.Format("Duplex Echo {0}: {1}", _messageCounter, _message));

    _messageCounter++;
    if (_messageCounter > 5)
        _timer.Dispose();
}

    #endregion
}

[ServiceContract]
public interface IDuplexClient
{
    [OperationContract(IsOneWay = true)]
    void ReturnEcho(string message);
}

The duplex config section:

<system.serviceModel>
<behaviors>
<serviceBehaviors>
<behavior name=”DuplexServerBehavior”>
<serviceMetadata httpGetEnabled=”true” />
<serviceDebug includeExceptionDetailInFaults=”false” />
</behavior>
</serviceBehaviors>
</behaviors>
<serviceHostingEnvironment aspNetCompatibilityEnabled=”true” />
<services>
<service behaviorConfiguration=”DuplexServerBehavior” name=”DuplexServer”>
<endpoint address=”” binding=”wsDualHttpBinding” contract=”DuplexServer” />
<endpoint address=”mex” binding=”mexHttpBinding” contract=”IMetadataExchange” />
</service>
</services>
</system.serviceModel>

I have setup a Duplex service in the client application as follows: 

        Binding svcBinding;
        EndpointAddress svcAddress;

        svcBinding = new PollingDuplexHttpBinding() { UseTextEncoding = true };
        svcAddress = new EndpointAddress("http://localhost/CTC.Test.WCF.Server/DuplexServer.svc");
        _duplex = new DuplexServerClient(svcBinding, svcAddress);

I have used a Simplex service in tandem with this, and calls to the Simplex service hit the breakpoints setup on the server and i can step through.

Calls to the Duplex service do not hit the breakpoints, although no error is raised on the client. If i inspect the HTTP traffic with Fiddler, i can see hundreds of 202 requests being fired after the initial request – i assume these are the polling requests.

Initial Duplex Request:

POST http://localhost/CTC.Test.WCF.Server/DuplexServer.svc HTTP/1.1
Accept: /
Content-Length: 665
Content-Type: application/soap+xml; charset=utf-8
UA-CPU: x86
Accept-Encoding: gzip, deflate
User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0; (R1 1.6); SLCC1; .NET CLR 2.0.50727; InfoPath.2; .NET CLR 3.5.21022; .NET CLR 3.5.30729; .NET CLR 3.0.30618)
Host: cotocovista4.cotoco.local
Connection: Keep-Alive
Pragma: no-cache

<s:Envelope xmlns:a=”http://www.w3.org/2005/08/addressing&#8221; xmlns:s=”http://www.w3.org/2003/05/soap-envelope”><s:Header><a:Action s:mustUnderstand=”1″>urn:IDuplexServer/SendEcho</a:Action><netdx:Duplex xmlns:netdx=”http://schemas.microsoft.com/2008/04/netduplex”><netdx:Address&gt;http://docs.oasis-open.org/ws-rx/wsmc/200702/anonymous?id=ae3e3139-0df8-41eb-97db-69c2c48782b7</netdx:Address><netdx:SessionId>43f9e320-cde3-4e21-a748-e5b29c10ee25</netdx:SessionId></netdx:Duplex><a:To s:mustUnderstand=”1″>http://cotocovista4.cotoco.local/CTC.Test.WCF.Server/DuplexServer.svc</a:To></s:Header><s:Body><SendEcho><message>Message!</message></SendEcho></s:Body></s:Envelope&gt;

Subsequent Duplex Requests:

POST http://localhost/CTC.Test.WCF.Server/DuplexServer.svc HTTP/1.1
Accept: /
Content-Length: 588
Content-Type: application/soap+xml; charset=utf-8
UA-CPU: x86
Accept-Encoding: gzip, deflate
User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0; (R1 1.6); SLCC1; .NET CLR 2.0.50727; InfoPath.2; .NET CLR 3.5.21022; .NET CLR 3.5.30729; .NET CLR 3.0.30618)
Host: cotocovista4.cotoco.local
Connection: Keep-Alive
Pragma: no-cache

<s:Envelope xmlns:a=”http://www.w3.org/2005/08/addressing&#8221; xmlns:s=”http://www.w3.org/2003/05/soap-envelope”><s:Header><a:Action s:mustUnderstand=”1″>http://docs.oasis-open.org/ws-rx/wsmc/200702/MakeConnection</a:Action><a:To s:mustUnderstand=”1″>http://cotocovista4.cotoco.local/CTC.Test.WCF.Server/DuplexServer.svc</a:To></s:Header><s:Body><wsmc:MakeConnection xmlns:wsmc=”http://docs.oasis-open.org/ws-rx/wsmc/200702″><wsmc:Address&gt;http://docs.oasis-open.org/ws-rx/wsmc/200702/anonymous?id=ae3e3139-0df8-41eb-97db-69c2c48782b7</wsmc:Address></wsmc:MakeConnection></s:Body></s:Envelope&gt;

Does anyone know why this would happen, i thought I’d finally sussed the last problem when it stopped throwing connection exceptions….

Regards

Tris

Update: I have tried recreating this in the following project types: WCF Application, Web Application, Web Project. I have succeeded in implementing the MS Example that uses WCF Message’s for the Duplex parameters without problem, but i was looking for a rapid way of assembling duplex web services using WSDL.

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1 Answer

  1. Editorial Team

    So – i managed to finally get it working using the following web config section, and adjusting the client side accordingly:

    <system.serviceModel>

<extensions>
  <bindingElementExtensions>
    <add name="pollingDuplex"
         type="System.ServiceModel.Configuration.PollingDuplexElement, System.ServiceModel.PollingDuplex"/>
  </bindingElementExtensions>
</extensions>

    <bindings>
        <customBinding>
            <binding name="DuplexConfig">
                <binaryMessageEncoding/>
                <pollingDuplex maxPendingSessions="2147483647" maxPendingMessagesPerSession="2147483647" inactivityTimeout="02:00:00" serverPollTimeout="00:05:00"/>
                <httpTransport/>
            </binding>
        </customBinding>
    </bindings>

    <behaviors>
        <serviceBehaviors>
            <behavior name="CTC.Test.WCF.Server.DuplexServiceBehavior">
                <serviceMetadata httpGetEnabled="true"/>
                <serviceDebug includeExceptionDetailInFaults="true"/>
                <serviceThrottling maxConcurrentSessions="2147483647"/>
            </behavior>
        </serviceBehaviors>
    </behaviors>

    <services>
        <service behaviorConfiguration="CTC.Test.WCF.Server.DuplexServiceBehavior" name="CTC.Test.WCF.Server.DuplexService">
            <endpoint address="" binding="customBinding" bindingConfiguration="DuplexConfig" contract="CTC.Test.WCF.Server.IDuplexService"/>
            <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange"/>
        </service>
    </services>

</system.serviceModel>

    If anyone can explain why this worked, but using wsDualHttpBinding did not, that would be really helpful. 🙂

    (Also – why is that displayed in a code block? :/ )

    Regards

    Tristan

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