Scanning Open Port

Use Nmap tool.

Typical types of port scanning:
A) TCP Connect scanning
nmap -v -sT localhost
nmap -v -sT 192.168.0.0/24

B) TCP SYN (half-open) scanning:
nmap -v -sS localhost
nmap -v -sS 192.168.0.0/24

C)TCP FIN scanning:
nmap -v -sF localhost
nmap -v -sF 192.168.0.0/24

D)TCP Xmas tree scanning
Useful to see if firewall protecting against this attack or not:
nmap -v -sX localhost
nmap -v -sX 192.168.0.0/24

F) TCP Null scanning
Useful to see if firewall protecting against this attack or not:
nmap -v -sN localhost
nmap -v -sN 192.168.0.0/24

G) TCP Windows scanning
nmap -v -sW localhost
nmap -v -sW 192.168.0.0/24

H) TCP RPC scanning
Useful to find out RPC (such as portmap) services
nmap -v -sR localhost
nmap -v -sR 192.168.0.0/24

I)UDP scanning
Useful to find out UDP ports
nmap -v -O localhost
nmap -v -O 192.168.0.0/24

J) Version scanning:
You can also find out what software version opening the port.
nmap -v -sV localhost
nmap -v -sV 192.168.0.0/24