ubuntu 16.04 trying to open port 8443 not working

Question

i need to open port 8443 in OS ubuntu 16.04 but nothing is working first i tried to do a scan port using Nmap:

RESULT :

Discovered open port 139/tcp on 127.0.0.1
Discovered open port 445/tcp on 127.0.0.1
Discovered open port 80/tcp on 127.0.0.1
Discovered open port 3306/tcp on 127.0.0.1
Discovered open port 22/tcp on 127.0.0.1
Discovered open port 902/tcp on 127.0.0.1

Then i open the port using ufw and a get the result :

8443/tcp                   ALLOW IN    Anywhere   
8443/tcp (v6)              ALLOW IN    Anywhere (v6)   

then i tried to display the open tcp port using :

netstat -ntlp | grep LISTEN

the result : not showing the port 8443

i will appreciate any help

Answer 1

The one that have to open the port is the application.

When you issue a netstat -ntlp you get something like this:

Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address               Foreign Address             State       PID/Program name
tcp        0      0 0.0.0.0:53                  0.0.0.0:*                   LISTEN      2955/dnsmasq
tcp        0      0 0.0.0.0:22                  0.0.0.0:*                   LISTEN      1515/sshd
tcp        0      0 127.0.0.1:25                0.0.0.0:*                   LISTEN      1684/master
tcp        0      0 0.0.0.0:4445                0.0.0.0:*                   LISTEN      2882/fop2_server
tcp        0      0 0.0.0.0:6050                0.0.0.0:*                   LISTEN      1763/perl
tcp        0      0 0.0.0.0:3306                0.0.0.0:*                   LISTEN      2763/mysqld

The last column (PID/Program name) shows the application that opened the port.

Assuming a port like a door to your system, then the thing that you did in ufw was like removing a lock in a door, so your application can easily open the door when it starts.