I'm still not sure whether we are on the same page. An error from curl isn't a big deal, as long as you can see the request arrive in nc.
It might be easier to do this instead of nc:
python -m SimpleHTTPServer 54321
and try the same curl.
Edit: and blah, I made errors earlier on. The curl needed to include :54321 in the URL. Too tired to be posting, apparently.