mexTcpBinding in WCF - IMetadataExchange errors - wcf

Question

I'm wanting to get a WCF-over-TCP service working. I was having some problems with modifying my own project, so I thought I'd start with the "base" WCF template included in VS2008.
Here is the initial WCF App.config and when I run the service the WCF Test Client can work with it fine:
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<system.web>
<compilation debug="true" />
</system.web>
<system.serviceModel>
<services>
<service name="WcfTcpTest.Service1" behaviorConfiguration="WcfTcpTest.Service1Behavior">
<host>
<baseAddresses>
<add baseAddress="http://localhost:8731/Design_Time_Addresses/WcfTcpTest/Service1/" />
</baseAddresses>
</host>
<endpoint address="" binding="wsHttpBinding" contract="WcfTcpTest.IService1">
<identity>
<dns value="localhost"/>
</identity>
</endpoint>
<endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange"/>
</service>
</services>
<behaviors>
<serviceBehaviors>
<behavior name="WcfTcpTest.Service1Behavior">
<serviceMetadata httpGetEnabled="True"/>
<serviceDebug includeExceptionDetailInFaults="True" />
</behavior>
</serviceBehaviors>
</behaviors>
</system.serviceModel>
</configuration>
This works perfectly, no issues at all.
I figured changing it from HTTP to TCP would be trivial: change the bindings to their TCP equivalents and remove the httpGetEnabled serviceMetadata element:
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<system.web>
<compilation debug="true" />
</system.web>
<system.serviceModel>
<services>
<service name="WcfTcpTest.Service1" behaviorConfiguration="WcfTcpTest.Service1Behavior">
<host>
<baseAddresses>
<add baseAddress="net.tcp://localhost:1337/Service1/" />
</baseAddresses>
</host>
<endpoint address="" binding="netTcpBinding" contract="WcfTcpTest.IService1">
<identity>
<dns value="localhost"/>
</identity>
</endpoint>
<endpoint address="mex" binding="mexTcpBinding" contract="IMetadataExchange"/>
</service>
</services>
<behaviors>
<serviceBehaviors>
<behavior name="WcfTcpTest.Service1Behavior">
<serviceDebug includeExceptionDetailInFaults="True" />
</behavior>
</serviceBehaviors>
</behaviors>
</system.serviceModel>
</configuration>
But when I run this I get this error in the WCF Service Host:
System.InvalidOperationException: The contract name 'IMetadataExchange' could not be found in the list of contracts implemented by the service Service1. Add a ServiceMetadataBehavior to the configuration file or to the ServiceHost directly to enable support for this contract.
I get the feeling that you can't send metadata using TCP, but that's the case why is there a mexTcpBinding option?

Answer 1

Well, if you want to have metadata - TCP or HTTP - you still need to include the serviceMetadata behavior!
<behaviors>
<serviceBehaviors>
<behavior name="WcfTcpTest.Service1Behavior">
<serviceDebug includeExceptionDetailInFaults="True" />
<serviceMetadata />
</behavior>
</serviceBehaviors>
</behaviors>
Sure, you can't have a "HttpGetEnabled" on it - but the behavior itself must be present in order to enable exchange of metadata (and thus the IMetadataExchange contract).