Using nmap

nmap (aka network mapper) is used to identify what ports are open for a given vm.

$ yum install nmap

then simply run:

$ nmap {ip-address}

or

$ nmap example.com

You can also scan a range of ip addresses:

$ nmap 192.168.1.1-100

nmap is useful if you want to quickly list out all open ports for localhost:

$ nmap localhost