nc -v -u -z -w 3 example.host 20-30
    Send UDP packets to ports 20-30 of example.host, and report which ones
    did not respond with an ICMP packet after three seconds.

something like

chchang@hqdc039:~/git$ nc -v -u -z -w 3 61.62.189.212 9993
Connection to 61.62.189.212 9993 port [udp/*] succeeded!
chchang@hqdc039:~/git$