Check Open Port(s) 

I usually use telnet, but if it’s not available but netcat (nc) is available:

nc -v -w 1 <IP_address_or_hostname> -z <Port_or_Range_of_ports>

So if I’d like to see whether port 20-22 is available on a fictitious hostname target.something.com

nc -v -w 1 target.something.com -z 20-22