WCF error : A registration already exists for URI - wcf

Question

Below is my WCF service configuration. I use 2 ServiceHost to host 2 service types. They use the same base address, but they use different relative addresses for their endpoints.
But I got this error, why?
Service cannot be started. System.InvalidOperationException: The ChannelDispatcher at 'http://earth:1111/' with contract(s) '"IHttpGetHelpPageAndMetadataContract"' is unable to open its IChannelListener. ---> System.InvalidOperationException: A registration already exists for URI 'http://earth:1111/'.
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<system.serviceModel>
<behaviors>
<serviceBehaviors>
<behavior name="serviceBehavior">
<serviceMetadata httpGetEnabled="true" />
</behavior>
</serviceBehaviors>
</behaviors>
<services>
<service behaviorConfiguration="serviceBehavior" name="Distributed.Troubleshooting.System.IIS.IISServiceType">
<endpoint address="iis" binding="basicHttpBinding" name="iis"
contract="Distributed.Troubleshooting.System.IIS.IISServiceContract" />
<endpoint address="iismex" binding="mexHttpBinding" bindingConfiguration=""
name="iismex" contract="IMetadataExchange" />
<host>
<baseAddresses>
<add baseAddress="http://Earth:1111/" />
</baseAddresses>
</host>
</service>
<service behaviorConfiguration="serviceBehavior" name="Distributed.Troubleshooting.System.SQL.SQLServiceType">
<endpoint address="sql" binding="basicHttpBinding" name="sql"
contract="Distributed.Troubleshooting.System.SQL.SQLServiceContract" />
<endpoint address="sqlmex" binding="mexHttpBinding" bindingConfiguration=""
name="sqlmex" contract="IMetadataExchange" />
<host>
<baseAddresses>
<add baseAddress="http://Earth:1111/" />
</baseAddresses>
</host>
</service>
</services>
</system.serviceModel>
</configuration>
Some even more ridiculous findings:
I changed my configuration to this:
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<system.serviceModel>
<behaviors>
<serviceBehaviors>
<behavior name="serviceBehavior">
<serviceMetadata httpGetEnabled="true" />
</behavior>
</serviceBehaviors>
</behaviors>
<services>
<service behaviorConfiguration="serviceBehavior" name="Distributed.Troubleshooting.System.IIS.IISServiceType">
<endpoint address="http://Earth:1111/iis" binding="basicHttpBinding" name="iis"
contract="Distributed.Troubleshooting.System.IIS.IISServiceContract" />
<endpoint address="http://Earth:1111/iismex" binding="mexHttpBinding" bindingConfiguration=""
name="iismex" contract="IMetadataExchange" />
<host>
<baseAddresses>
<add baseAddress="http://Earth:1111/iis" />
</baseAddresses>
</host>
</service>
<service behaviorConfiguration="serviceBehavior" name="Distributed.Troubleshooting.System.SQL.SQLServiceType">
<endpoint address="http://Earth:1111/sql" binding="basicHttpBinding" name="sql"
contract="Distributed.Troubleshooting.System.SQL.SQLServiceContract" />
<endpoint address="http://Earth:1111/sqlmex" binding="mexHttpBinding" bindingConfiguration=""
name="sqlmex" contract="IMetadataExchange" />
<host>
<baseAddresses>
<add baseAddress="http://Earth:1111/sql" />
</baseAddresses>
</host>
</service>
</services>
</system.serviceModel>
</configuration>
Then I found I can use "Add Service Reference" in Visual Studio with the following addresses:
http://Earth:1111/iis
http://Earth:1111/iismex
http://Earth:1111/sql
http://Earth:1111/sqlmex

Answer 1

It is possible to host more than one Service with the same base address. Set the HttpHelpPageEnabled and the HttpsHelpPageEnabled properties of all ServiceDebugBehaviors to false, then it should work.
Atention: By default, there's always a ServiceDebugBehavior registered in the behavior's description collection of a host even if it is not specified explicitely (I tried it only with programatic configration and the ServiceHost class, not via XML config). So, you should add an explicit ServiceDebugBehavior and set the mentioned properties. The IncludeExceptionDetailInFaults property can be true.

Answer 2

Have you tried removing one of the Service blocks and combining the endpoints into one?
I cant see any reason why you have them seperated.
Make sure the baseaddress + endpoint address are unique.

Answer 3

You can't host two services with the same base address.
You need to host the other one on a different port or address.
Something like
http://Earth:1111/Service1
and
http://Earth:1111/Service2

Answer 4

I don't really know why this is the case but one solution is to leave the service with no base address and to specify the full address for the endpoints. This doesn't change the address of the different endpoints, nor the addresses unicity. I could not find any relevant reference for this on MSDN.
From my own experience, the problem appears with http and not with net.tcp. I am not using service metadata. I thought the "IHttpGetHelpPageAndMetadataContract" has to do with metadata but found no way to disable it.

Answer 5

You'll also get this error if you accidentally start the same service twice rather than start the two different services.