the nufw server has no configuration file as it as only a restricted set of options :
nufw [-nCMhVv[v[v[v[v[v[v[v[v[v]]]]]]]]]] [-l local_port] [-L local_addr] [-d remote_addr] [-p remote_port] [-L queue_maxlen] [-t packet_timeout] [-T track_size] [-n DN name]
-h : display this help and exit
-v : increase verbosity (maximum 9)
-V : display version and exit
-D : daemonize
-k : Use specified file as key file
-c : Use specified file as cert file
-a : Use specified file as ca file (strict check on server certificate is done if activated)
-U : use UDP unencrypted communication with nuauth server
-v : increase debug level (+1 for each 'v') (max useful number : 10)
-m : mark packet with userid
-L : specify queue maximum length (default: 1024)
-d : remote address we send auth requests to (adress of the nuauth server) (default : 127.0.0.1)
-p : remote port we send auth requests to (TCP port nuauth server listens on) (default : 4128)
-t : timeout to forget about packets when they don't match (default : 15 s)
-T : track size (default : 1000)
-n : Check nuauth certificate DN against the specified string
-C : send conntrack destroy event to nuauth
-M : only report event on marked connections to nuauth (implies -C and - m)