jQuery/Ajax cross domain issue and CORS

I have a Ajax client forwarding requests to a node.js server running
on the IBM i. However, as expected, I get the "No
Access-Control-Allow-Origin header on the requested resource" error.

This is due my laptop client app being in a different domain to the
node.js server on the i. Although both domains are within our estate.

I don't want to go the inelegant JSONP route with the call back but
would prefer to control from the i via CORS but has anyone done this
and be prepared to share some detail?

Thanks,

Keith