Loophole

Congratulations, your tunnel is up and running!

However... it looks like the application you're trying to expose is not available.

Original error: dial tcp 127.0.0.1:3000: connect: connection refused

This request would normally end up with 502 status code.
If that's what you intended please restart the tunnel with --disable-proxy-error-page option
to remove this page and get regular 502 error.