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Asked: 2026-05-13T23:28:36+00:00

I am trying to enable an additional net.tcp endpoint (which uses Username authentication) for

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I am trying to enable an additional net.tcp endpoint (which uses Username authentication) for an existing WCF service. The service is hosted in IIS7.

Executing a client against the service returns an error that the socket connection was aborted. Enabling tracing against the service reveals the following exception is thrown:

System.ArgumentOutOfRangeException
The value of this argument must be positive.
Parameter name: maxAccepts
Actual value was 0.

I’m confused, because as best I can tell port sharing should be disabled by the configuration (see below), but it’s still calling through the port sharing code (again, as best I can tell). In any case, I can’t find any way to specify this maxAccepts value; Google doesn’t know anything about it, and the maxPendingAccepts value doesn’t seem to do it. How do I resolve the error?

The service’s config file contains the following for the net.tcp endpoint:

<bindings>
  <customBinding>
    <binding name="netTcp">
      <security authenticationMode="UserNameOverTransport" />
      <windowsStreamSecurity />
      <tcpTransport portSharingEnabled="false" listenBacklog="10" maxPendingAccepts="10" maxPendingConnections="10" />
    </binding>
  </customBinding>
</bindings>
<behaviors>
  <serviceBehaviors>
    <behavior name="netTcp">
      <serviceDebug includeExceptionDetailInFaults="false" />
      <serviceMetadata/>
      <serviceCredentials>
        <userNameAuthentication userNamePasswordValidationMode="Custom" customUserNamePasswordValidatorType="Asi.Soa.ServiceModelEx.NullUserNamePasswordValidator, Asi.Soa.ServiceModelEx" />
        <clientCertificate>
          <authentication certificateValidationMode="None"/>
        </clientCertificate>
      </serviceCredentials>
      <serviceAuthorization principalPermissionMode="Custom">
        <authorizationPolicies>
          <add policyType="Asi.Soa.ServiceModelEx.ClaimsAuthorizationPolicy, Asi.Soa.ServiceModelEx" />
        </authorizationPolicies>
      </serviceAuthorization>
    </behavior>
  </serviceBehaviors>
</behaviors>

The full exception stack trace is:

System.ServiceModel.Channels.ConnectionAcceptor..ctor(IConnectionListener listener, Int32 maxAccepts, Int32 maxPendingConnections, ConnectionAvailableCallback callback, ErrorCallback errorCallback)
System.ServiceModel.Channels.ConnectionDemuxer..ctor(IConnectionListener listener, Int32 maxAccepts, Int32 maxPendingConnections, TimeSpan channelInitializationTimeout, TimeSpan idleTimeout, Int32 maxPooledConnections, TransportSettingsCallback transportSettingsCallback, SingletonPreambleDemuxCallback singletonPreambleCallback, ServerSessionPreambleDemuxCallback serverSessionPreambleCallback, ErrorCallback errorCallback)
System.ServiceModel.Channels.SharedTcpTransportManager.CreateConnectionDemuxer()
System.ServiceModel.Channels.SharedTcpTransportManager.OnDuplicatedVia(Uri via, Int32&amp; connectionBufferSize)
System.ServiceModel.Channels.SharedConnectionListener.SharedListenerProxy.HandleOnVia(DuplicateContext duplicateContext)
System.ServiceModel.Channels.SharedConnectionListener.SharedListenerProxy.System.ServiceModel.Activation.IConnectionDuplicator.BeginDuplicate(DuplicateContext duplicateContext, AsyncCallback callback, Object state)
AsyncInvokeBeginBeginDuplicate(Object , Object[] , AsyncCallback , Object )
System.ServiceModel.Dispatcher.AsyncMethodInvoker.InvokeBegin(Object instance, Object[] inputs, AsyncCallback callback, Object state)
System.ServiceModel.Dispatcher.DispatchOperationRuntime.InvokeBegin(MessageRpc&amp; rpc)
System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage5(MessageRpc&amp; rpc)
System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage4(MessageRpc&amp; rpc)
System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage3(MessageRpc&amp; rpc)
System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage2(MessageRpc&amp; rpc)
System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage1(MessageRpc&amp; rpc)
System.ServiceModel.Dispatcher.MessageRpc.Process(Boolean isOperationContextSet)
System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.Dispatch(MessageRpc&amp; rpc, Boolean isOperationContextSet)
System.ServiceModel.Dispatcher.ChannelHandler.DispatchAndReleasePump(RequestContext request, Boolean cleanThread, OperationContext currentOperationContext)
System.ServiceModel.Dispatcher.ChannelHandler.HandleRequest(RequestContext request, OperationContext currentOperationContext)
System.ServiceModel.Dispatcher.ChannelHandler.AsyncMessagePump(IAsyncResult result)
System.ServiceModel.Dispatcher.ChannelHandler.OnAsyncReceiveComplete(IAsyncResult result)
System.ServiceModel.Diagnostics.Utility.AsyncThunk.UnhandledExceptionFrame(IAsyncResult result)
System.ServiceModel.AsyncResult.Complete(Boolean completedSynchronously)
System.ServiceModel.Channels.FramingDuplexSessionChannel.TryReceiveAsyncResult.OnReceive(IAsyncResult result)
System.ServiceModel.Diagnostics.Utility.AsyncThunk.UnhandledExceptionFrame(IAsyncResult result)
System.ServiceModel.AsyncResult.Complete(Boolean completedSynchronously)
System.ServiceModel.Channels.SynchronizedMessageSource.ReceiveAsyncResult.OnReceiveComplete(Object state)
System.ServiceModel.Channels.SessionConnectionReader.OnAsyncReadComplete(Object state)
System.ServiceModel.Channels.TracingConnection.TracingConnectionState.ExecuteCallback()
System.ServiceModel.Channels.TracingConnection.WaitCallback(Object state)
System.ServiceModel.Channels.PipeConnection.OnAsyncReadComplete(Boolean haveResult, Int32 error, Int32 numBytes)
System.ServiceModel.Channels.OverlappedContext.CompleteCallback(UInt32 error, UInt32 numBytes, NativeOverlapped* nativeOverlapped)
System.ServiceModel.Diagnostics.Utility.IOCompletionThunk.UnhandledExceptionFrame(UInt32 error, UInt32 bytesRead, NativeOverlapped* nativeOverlapped)
System.Threading._IOCompletionCallback.PerformIOCompletionCallback(UInt32 errorCode, UInt32 numBytes, NativeOverlapped* pOVERLAP)

Edit: I have installed the non-HTTP WCF activation components, run ServiceModelReg.exe, added net.tcp and net.pipe to the list of enabled protocols in IIS Manager, etc. No joy.

I’ve also written a quick Windows Service to host the service (not the ideal long-term solution for us), and the Net TCP connection works fine there, so it doesn’t appear to be anything in my configuration or code, which means something isn’t right in/with IIS. Does the app pool for the application have to be running in Integrated mode? I tried it both ways, it didn’t seem to make a difference, but our app currently is installed in Classic mode.

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1 Answer

  1. Editorial Team

    As best I can determine, the problem is simply that .NET does not like hosting two services in the same IIS application when one is a Soap11 endpoint and one is a NetTcp endpoint. Removing the Soap11 endpoint allows the NetTcp endpoint to work without error.

    We’ve moved to a model where we are using a Windows Service to host the NetTcp endpoint and left the Soap11 endpoint in IIS.

    If anyone figures out how to host both a NetTcp and Soap11 service in the same application in IIS, I’d love to hear about it.

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