Checking ports with netcat
From thelinuxwiki
checking udp ports
~% nc -vzu 192.168.1.1 53
examplehostname [192.168.1.1] 53 (domain) open
~% nc -vzu 192.168.1.1 54
examplehostname [192.168.1.1] 54 (?) : Connection refused
checking tcp ports
~% nc -vz 192.168.1.1 80
examplehostname [192.168.1.1] 80 (http) open
~% nc -vzu 192.168.1.1 80
examplehostname [192.168.1.1] 80 (http) : Connection refused ~
