How to solve 'A registration already exists for URI http://localhost:42444/Harp'

[Jason Hamilton]

Hey all,

I have one of those strange issues where I swear I haven't run this code in two weeks and it was working perfectly when I ran it last but now I get an exception that I have not only never seen before, but can't figure out how to fix either.
I have built a WCF server application to handle passing data that is processed in native code to an ASP page (which is something that WCF is very good at), but when I try to open the ServiceHost object now, I get an exception that reads:

"The ChannelDispatch er at 'http://localhost:42444/Harp/' with contract(s) '"IHarpWCF"' is unable to open its IChannelListene r."

Then after two more InnerExceptions (identical but pertaining to contract(s) '"IssueAndRenew Session"' and '"SecurityNegot iationContract" ' there was one that read:

"A registration already exists for URI 'http://localhost:42444/Harp/'."

The code that is throwing looks like:

Private Sub StartBtn_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles StartBtn.Click
        'My.Settings.TargetDB = TargetDBEdit.Text
        'My.Settings.TargetHTML = TargetHTMLEdit.Text
        'My.Settings.OutputDir = OutputDirEdit.Text
        service = New ServiceHost(GetType(Harp_WCF.HARP_WCF))
        HarpWCF = Harp_WCF.HARP_WCF.Instance()
 
        service.Open()
    End Sub
 

So the question is: what does this exception mean? Why have I never seen it before? And what do I do to make it go away?

It implies that the URI is already registered... well yes, but this program. There isn't another instance already running anywhere...

Just for the sake of completeness, here is the serviceModel section of the app.config file...

<system.serviceModel>
    <services>
      <service name="Harp_WCF.HARP_WCF" behaviorConfiguration="Harp_WCF.Service1Behavior">
        <host>
          <baseAddresses>
            <add baseAddress="http://localhost:42444/Harp/"   />
          </baseAddresses>
        </host>
        <!-- Service Endpoints -->
        <!-- Unless fully qualified, address is relative to base address supplied above -->
        <endpoint address=""  binding="wsHttpBinding" contract="Harp_WCF.IHarpWCF" name="HTTPEndpoint">
          <!-- 
              Upon deployment, the following identity element should be removed or replaced to reflect the 
              identity under which the deployed service runs.  If removed, WCF will infer an appropriate identity 
              automatically.
          -->
          <identity>
            <dns value="localhost"/>
          </identity>
        </endpoint>
        <!-- Metadata Endpoints -->
        <!-- The Metadata Exchange endpoint is used by the service to describe itself to clients. -->
        <!-- This endpoint does not use a secure binding and should be secured or removed before deployment -->
        <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange"/>
      </service>
    </services>
    <behaviors>
      <serviceBehaviors>
        <behavior name="Harp_WCF.Service1Behavior">
          <!-- To avoid disclosing metadata information, 
          set the value below to false and remove the metadata endpoint above before deployment -->
          <serviceMetadata httpGetEnabled="True"/>
          <!-- To receive exception details in faults for debugging purposes, 
          set the value below to true.  Set to false before deployment 
          to avoid disclosing exception information -->
          <serviceDebug includeExceptionDetailInFaults="False" />
        </behavior>
      </serviceBehaviors>
    </behaviors>
  </system.serviceModel>