this will use the port to run getinfo command by running the generic curl utility.
curl --user user:pass --data-binary '{"jsonrpc": "1.0", "id":"curltest", "method": "getinfo"}' http://127.0.0.1:7890/
(change user and pass to the ones in nu.conf. make sure you set server=1).
if it returns results in json format, your nu is working as a server as seen by other programs on the same computer.
try that with ppcoind
curl --user user:pass --data-binary '{"jsonrpc": "1.0", "id":"curltest", "method": "getinfo"}' http://127.0.0.1:9902/
to show that it too is able to respond to rpc calls.
btw you can set rpcport=9999 in conf and above command line to see if it makes any differences. used to help me to debug.