WCF PollingDuplexHttpBinding与Silverlight客户端超时和错误

Question

我正在构建一个WPF 3.5桌面应用程序，它有一个自我托管的WCF服务。

该服务有一个PollingDuplexHttpBinding端点，定义如下：

public static void StartService()
    {
        var selfHost = new ServiceHost(Singleton, new Uri("http://localhost:1155/"));

        selfHost.AddServiceEndpoint(
            typeof(IMyService), 
            new PollingDuplexHttpBinding(PollingDuplexMode.MultipleMessagesPerPoll) {ReceiveTimeout = new TimeSpan(1,0,0,0)},
            "MyService"
        );

        ServiceMetadataBehavior smb = new ServiceMetadataBehavior();
        smb.HttpGetEnabled = true;
        selfHost.Description.Behaviors.Add(smb);

        selfHost.AddServiceEndpoint(typeof(IPolicyRetriever), new WebHttpBinding(), "").Behaviors.Add(new WebHttpBehavior());

        selfHost.Open();
    }

注意: IPolicyRetriever是一个使我能够定义策略文件的服务。

这是可行的，我可以在我的客户端Silverlight应用程序中看到我的服务。然后，在Silverlight代码中创建对代理的引用，如下所示：

        EndpointAddress address = new EndpointAddress("http://localhost:1155/MyService");

        PollingDuplexHttpBinding binding = new PollingDuplexHttpBinding(PollingDuplexMode.MultipleMessagesPerPoll);
        binding.ReceiveTimeout = new TimeSpan(1, 0, 0, 0);
        _proxy = new MyServiceClient(binding, address);
        _proxy.ReceiveReceived += MessageFromServer;
        _proxy.OrderAsync("Test", 4);

而且这也很好，沟通也很有效！

但是，如果我把它放在一边(即不要从服务器发送消息)超过1分钟，那么尝试从WPF服务器应用程序向客户端发送一条消息，我会得到如下所示的超时错误：

试图在00:01:00之后发送的IOutputChannel超时。增加传递给调用的超时值，以发送或增加绑定上的SendTimeout值。分配给此操作的时间可能是较长超时的一部分。。

它全部在本地主机上运行，不应该有延迟，更不用说1分钟的延迟了。我不知道为什么，但是这个频道好像关闭了或者消失了什么的.

我还尝试删除绑定上的超时，并得到这样的错误

通信对象System.ServiceModel.Channels.ServiceChannel不能用于通信，因为它已被中止。

我怎么才能找出这里出了什么问题？

Answer 1

WPF使用wsDualHttpBinding，Silverlight轮询双工.WPF解决方案很简单；Silverlight需要ServiceHostFactory和更多代码。另外，Silverlight Server从不发送消息，而是客户端轮询服务器并检索其消息。

在PollingDuplexHttpBinding出现了许多问题之后，我决定使用没有MultipleMessagesPerPoll的CustomBinding。

web.config

<system.serviceModel>
    <behaviors>
        <serviceBehaviors>
            <behavior name="SlApp.Web.DuplexServiceBehavior">
                <serviceMetadata httpGetEnabled="true" />
                <serviceDebug includeExceptionDetailInFaults="true" />
            </behavior>
        </serviceBehaviors>
    </behaviors>

  <serviceHostingEnvironment aspNetCompatibilityEnabled="true" multipleSiteBindingsEnabled="true" />

    <services>
        <service behaviorConfiguration="SlApp.Web.DuplexServiceBehavior" name="SlApp.Web.DuplexService">
            <endpoint address="WS" binding="wsDualHttpBinding" contract="SlApp.Web.DuplexService" />
            <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange" />
        </service>
    </services>      
</system.serviceModel>

DuplexService.svc：

<%@ ServiceHost Language="C#" Debug="true" Service="SlApp.Web.DuplexService" Factory="SlApp.Web.DuplexServiceHostFactory" %>

DuplexServiceHostFactory.cs：

    public class DuplexServiceHostFactory : ServiceHostFactoryBase
    {
        public override ServiceHostBase CreateServiceHost(string constructorString, Uri[] baseAddresses)
        {
            return new DuplexServiceHost(baseAddresses);
        }
    }

    class DuplexServiceHost : ServiceHost
    {
        public DuplexServiceHost(params Uri[] addresses)
        {
            base.InitializeDescription(typeof(DuplexService), new UriSchemeKeyedCollection(addresses));
        }

        protected override void InitializeRuntime()
        {
            PollingDuplexBindingElement pdbe = new PollingDuplexBindingElement()
            {
                ServerPollTimeout = TimeSpan.FromSeconds(3),
                //Duration to wait before the channel is closed due to inactivity
                InactivityTimeout = TimeSpan.FromHours(24)
            };

            this.AddServiceEndpoint(typeof(DuplexService),
                new CustomBinding(
                    pdbe,
                    new BinaryMessageEncodingBindingElement(),
                    new HttpTransportBindingElement()), string.Empty);

            base.InitializeRuntime();
        }
    }

Silverlight客户端代码：

address = new EndpointAddress("http://localhost:43000/DuplexService.svc");
binding = new CustomBinding(
            new PollingDuplexBindingElement(),
            new BinaryMessageEncodingBindingElement(),
            new HttpTransportBindingElement()
        );
proxy = new DuplexServiceClient(binding, address);