Simple Port Scan with NMap

Port Scan's don't only need to be the tool for hackers, they area a handy tool for a network or server administrator. Especially when debugging firewall issues. For example want to see which TCP ports www.google.com has open?

nmap -sT www.google.com

The output of the simple example above might look something like this:

Interesting ports on py-in-f104.google.com (64.233.167.104):
(The 1657 ports scanned but not shown below are in state: filtered)
PORT    STATE  SERVICE
80/tcp  open   http
179/tcp closed bgp
443/tcp open   https

Nmap run completed -- 1 IP address (1 host up) scanned in 31.619 seconds

That shows port 80, 179, and 443 open, so if your trying to ssh into google.com you won't get very far.