nmap for scanning port on linux

You can use nmap tool for this job. it's versatile in specifying targets. User will scan entire network or selected  host or single server. Nmap is additionally helpful to check your firewall rules. namp is metwork exploration tool and security / port scanner. 

in step with nmap man page: It is AN open supply tool for network exploration and security auditing. it had been designed to quickly scan massive networks, though it works fine against single hosts. Nmap uses raw information processing packets in novel ways in which to see what hosts square measure on the market on the network. 

what services (application name and version) those hosts square measure providing, what operative systems (and OS versions) they're running, what form of packet filters/firewalls square measure in use, and dozens of alternative characteristics. whereas Nmap is often used for security audits, several systems and network directors realize it helpful for routine tasks like network inventory, managing service upgrade schedules, and observation host or service period.

see how to use nmap for scaning port on linux  
nmap use for scaning tcp connection from the localhost and network 168.124.0/024 and 192.168.10.0/24

# nmap -v -sT 168.124.0/024
# nmap -v -sT 192.168.10.0/24

nmap use for scanning half open port on network 168.124.0/024 and 192.168.10.0/24

# nmap -v -sS 168.124.0/024
# nmap -v -sS 192.168.10.0/24

nmap use for scanning TCP FIN scanning

# nmap -v -sF 168.124.0/024
# nmap -v -sF 192.168.10.0/24

nmap TCP Xmas tree scanning

Useful to see if firewall protecting against this kind of attack or not:
# nmap -v -sX 168.124.0/024
# nmap -v -sX 192.168.10.0/24

nmap TCP Null scanning

Useful to see if firewall protecting against this kind attack or not:
# nmap -v -sN 168.124.0/024
# nmap -v -sN 192.168.10.0/24
nmap TCP Windows scanning

# nmap -v -sW 168.124.0/024
# nmap -v -sW 192.168.10.0/24
nmap TCP RPC scanning

Useful to find out RPC (such as portmap) services
# nmap -v -sR 168.124.0/024
# nmap -v -sR 192.168.10.0/24
nmap UDP scanning

Useful to find out UDP ports
# nmap -v -O 168.124.0/024
# nmap -v -O 192.168.10.0/24
nmap remote software version scanning

You can also find out what software version opening the port.
# nmap -v -sV 168.124.0/024
# nmap -v -sV 192.168.10.0/24

all rule above is use for scanning vuln on the server or the network that make intruder for linux security