If your application employs dual HTTP Binding, since HTTP is inherently not a duplex protocol, the framework uses a standard port to receive response data being passed to the callback. When you attempt to run multiple instances of your application, you may be unable to do so using the same port number. VuGen provides you with an option of replacing the original client base address's port number with a unique port.
When you enable the Generate Unique Client Base Address recording option, VuGen checks the type of communication used by the application. If it detects dual HTTP communication, WSDualHttpBinding, it runs the FindPort utility (provided in LrReplayUtils) in the Helper file and finds unique ports for each instance of the callback.
This option is enabled by default. It is only relevant when you enable the above option, Generate dummy callback handler.
When you enable this option, VuGen generates the following code in the script:
#warning: Code Generation Warning // Override the original client base address with a unique port number DualProxyHelper.SetUniqueClientBaseAddress<XXXX>(YYYYY);
For more information, see Microsoft .NET > Recording - Recording Options.