Question

So I have the following setup:

• a VB6 Application using a .NET dll on the one hand
• a .NET Service on the other end

The VB6 application uses a small interface dll to communicate to our new infrastructure (servies etc) and can hardly be changed in functionality. We choose to use WCF with a binding like this

<system.serviceModel>
    <client>
      <endpoint address="net.tcp://localhost:8001/HostCommunicator" binding="netTcpBinding" bindingConfiguration="NETTcpBinding" contract="IHostCommunicationContract"/>
    </client>

    <bindings>
      <netTcpBinding>
        <binding name="NETTcpBinding" maxBufferPoolSize="2147483647" maxBufferSize="2147483647" maxReceivedMessageSize="2147483647" receiveTimeout="00:10:00" sendTimeout="00:10:00">
          <readerQuotas maxDepth="2147483647" maxStringContentLength="2147483647" maxArrayLength="2147483647" maxBytesPerRead="2147483647" maxNameTableCharCount="2147483647"/>
          <reliableSession ordered="true" inactivityTimeout="00:10:00" enabled="false"/>
          <security mode="Transport">
            <transport clientCredentialType="Windows" />
          </security>
        </binding>
      </netTcpBinding>
    </bindings>
</system.serviceModel>
  <startup>

to communicate.

This works fine and fast for single requests but one mode of the VB6 Application is a kind of batch mode where it sends an individual request for each file it processes. There will be about 1-4 requests per second.

This works fine until a number of requests is done. On my current machine and software version this are 50 requests. If I start the VB6 application over it does 50 requests again. After the limit the application hangs at 99% CPU usage.

We are using a duplex channel contract.

Answer 1

Have you remembered to close your connections? It looks like you are not closing the connections, just opening new ones for each request?