nmap

ever wonder what the IP address of that server in the corner is, you could always try scanning your network for computers using nmap.

sudo apt-get install nmap

to scan for running computers, here using sudo is optional but will provide more information, all others require root privileges

<sudo> nmap -sP 192.168.1.1/24

to scan for open ports on a computer

sudo nmap -sS 192.168.1.1/24

to include open ports and operating system information

sudo nmap -O 192.168.1.1/24