By default nmap performs a TCP scan only. I’ll show you how to scan for UDP ports with nmap!
The syntax is
$ sudo nmap -sU -p port target
$ sudo nmap -sU -p 3478 192.168.1.25 Starting Nmap 6.00 ( http://nmap.org ) at 2012-06-13 20:43 EDT Nmap scan report for example.com (192.168.1.25) Host is up (0.096s latency). PORT STATE SERVICE 3478/udp open|filtered unknown Nmap done: 1 IP address (1 host up) scanned in 1.17 seconds
Note that UDP scanning is problematic because of the lack of a confirming SYN-ACK or other packet as with TCP. As such, many false positives can occur from UDP port scans.