how to check open ports in ubuntu using nmap
first install nmap
# sudo apt install nmap
then type this command to check open ports.
# nmap -sT -O localhost
result look like this,
root@host:~# nmap -sT -O localhost
Starting Nmap 7.80 ( https://nmap.org ) at 2022-04-30 16:28 EDT
Nmap scan report for localhost (127.0.0.1)
Host is up (0.00015s latency).
Not shown: 982 closed ports
PORT STATE SERVICE
21/tcp open ftp
22/tcp open ssh
25/tcp open smtp
53/tcp open domain
80/tcp open http
110/tcp open pop3
143/tcp open imap
443/tcp open https
465/tcp open smtps
587/tcp open submission
631/tcp open ipp
993/tcp open imaps
995/tcp open pop3s
3306/tcp open mysql
8000/tcp open http-alt
8081/tcp open blackice-icecap
10024/tcp open unknown
10025/tcp open unknown
Device type: general purpose
Running: Linux 2.6.X
OS CPE: cpe:/o:linux:linux_kernel:2.6.32
OS details: Linux 2.6.32
Network Distance: 0 hops
OS detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 2.11 seconds
But if you want to check open ports from other side.
for TCP ports check
# nc -z -v localhost 1-65535 2>&1 | grep succeeded
here is the result
akwal:/# nc -z -v localhost 1-65535 2>&1 | grep succeeded
Connection to localhost 21 port [tcp/ftp] succeeded!
Connection to localhost 22 port [tcp/ssh] succeeded!
Connection to localhost 25 port [tcp/smtp] succeeded!
Connection to localhost 80 port [tcp/http] succeeded!
Connection to localhost 443 port [tcp/https] succeeded!
Connection to localhost 3306 port [tcp/mysql] succeeded!
for UDP ports check add -u
akwal:/# nc -z -v -u localhost 1-65535 2>&1 | grep succeeded
Connection to localhost (::1) 53 port [udp/domain] succeeded!
Connection to localhost (::1) 123 port [udp/ntp] succeeded!
That's it,
