Question

I recently installed the new .NET Framework 4.5 (previously was 4.0 installed) on my Server and I´m getting a System.ServiceModel.AddressAlreadyInUseException when I start my Windows Service that exposes WCF endpoints.

System.ServiceModel.AddressAlreadyInUseException: There is already a
listener on IP endpoint 0.0.0.0:56543. This could happen if there is
another application already listening on this endpoint or if you have
multiple service endpoints in your service host with the same IP
endpoint but with incompatible binding configurations. —>
System.Net.Sockets.SocketException: Only one usage of each socket
address (protocol/network address/port) is normally permitted at
System.Net.Sockets.Socket.DoBind(EndPoint endPointSnapshot,
SocketAddress socketAddress) at
System.Net.Sockets.Socket.Bind(EndPoint localEP) at
System.ServiceModel.Channels.SocketConnectionListener.Listen() —
End of inner exception stack trace — at
System.ServiceModel.Channels.SocketConnectionListener.Listen() at
System.ServiceModel.Channels.BufferedConnectionListener.Listen() at
System.ServiceModel.Channels.ExclusiveTcpTransportManager.OnOpen()
at
System.ServiceModel.Channels.TransportManager.Open(TransportChannelListener
channelListener) at
System.ServiceModel.Channels.TransportManagerContainer.Open(SelectTransportManagersCallback
selectTransportManagerCallback) at
System.ServiceModel.Channels.TransportChannelListener.OnOpen(TimeSpan
timeout) at
System.ServiceModel.Channels.ConnectionOrientedTransportChannelListener.OnOpen(TimeSpan
timeout) at
System.ServiceModel.Channels.TcpChannelListener`2.OnOpen(TimeSpan
timeout) at
System.ServiceModel.Channels.CommunicationObject.Open(TimeSpan
timeout) at
System.ServiceModel.Dispatcher.ChannelDispatcher.OnOpen(TimeSpan
timeout) at
System.ServiceModel.Channels.CommunicationObject.Open(TimeSpan
timeout) at System.ServiceModel.ServiceHostBase.OnOpen(TimeSpan
timeout) at
System.ServiceModel.Channels.CommunicationObject.Open(TimeSpan
timeout) at Qosit.Infrastructure.UnisServer.OnStart(String[] args)

The configuration of my WCF endpoints looks like that:

<system.serviceModel>
    <bindings>
      <netTcpBinding>
        <binding name="NetTcpBindingConfiguration" closeTimeout="00:01:00" openTimeout="00:01:00" receiveTimeout="00:10:00" sendTimeout="00:01:00" transactionFlow="false" transferMode="Buffered" transactionProtocol="OleTransactions" hostNameComparisonMode="StrongWildcard" listenBacklog="10" maxBufferPoolSize="524288" maxBufferSize="65536" maxConnections="10" maxReceivedMessageSize="65536">
          <readerQuotas maxDepth="32" maxStringContentLength="5242880" maxArrayLength="16384" maxBytesPerRead="4096" maxNameTableCharCount="16384" />
          <reliableSession ordered="true" inactivityTimeout="00:10:00" enabled="false" />
        </binding>
      </netTcpBinding>
    </bindings>
    <behaviors>
      <serviceBehaviors>
        <behavior name="">
          <serviceDebug includeExceptionDetailInFaults="true" />
        </behavior>
        <behavior name="MEX">
          <serviceMetadata/>
        </behavior>
      </serviceBehaviors>
    </behaviors>
    <services>
      <service behaviorConfiguration="MEX" name="MyAssembly.MyNamespace.MyService">      
        <endpoint address="net.tcp://localhost:56543/MyService"
          binding="netTcpBinding" bindingConfiguration="NetTcpBindingConfiguration" contract="MyAssembly.MyNamespace.MyServiceInterface" />
        <endpoint address="net.tcp://localhost:56543/MEX" binding="mexTcpBinding"
          contract="IMetadataExchange" />
      </service>
    </services>
  </system.serviceModel>

I think it has something to do with the MEX endpoint that uses the same port, but I’m not sure how to configure it correctly after upgrading to .NET Framework 4.5.

Was there a change in WCF so that these configuration raises an exception?

Answer 1

This is because of some limitations in using the same port for both the netTcp endpoint and mex endpoint documented here refer section “Sharing a port between a service endpoint and a mex endpoint using the NetTcpBinding”. In 4.0 the defaults for listenBackLog and MaxConnections were 10. In 4.5 these defaults were revised as 12 * ProcessorCount. This exception happens when you try to share a port between netTcpBinding and mex endpoint provided you have different values for these two properties. In 4.0 this worked fine as you have set these to the default values (10) and thus these settings do not differ on both endpoints. But in 4.5 these are left as 10 for netTcp endpoint, but computed as 12* ProcessorCount. So the exception.

To solve this issue there are 2 ways:

1. Remove these settings (listenBackLog and MaxConnections) from the config. In this way you will get a default of 12 * Processor count automatically which is > than 4.0 defaults.
2. Follow the work around of configuring mex endpoint on a different port as described in documentation

Please check out this blog for more details.