nc command from your terminal, you can scan a port, or a range of ports, to verify whether a UDP port is open and able to receive traffic.
This first command will scan all of the UDP ports from 1 to 65535 and add the results to a text file:
nc -vnzu server.ip.address.here 1-65535 > udp-scan-results.txt
This merely tells you that the UDP ports are open and able receive traffic.
Perhaps a more revealing test would be to actually transfer a file using UDP.