WCF Net.TCP service throwing obscure errors

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.