I think your issue is you don't have the Splunk Web interface up and running yet. or is this the error you get back from the client that you are indexing, or in your splunkd logs?
The Webping app has been updated many time since your post, I'd also try and get the new version.
I'm not sure what "webping" is. Can you update your question and add the exact URL that your browser is pointing to? (Click the "update" link below your question.)