find out what is listening on a port code example

Example 1: check which application is using port

In Windows CMD/Powershell:
netstat -aon | findstr '[port_number]'

Example 2: how to check listening ports on a server

$ sudo netstat -plnt
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address               Foreign Address             State       PID/Program name
tcp        0      0 0.0.0.0:3306                0.0.0.0:*                   LISTEN      3686/mysqld
tcp        0      0 :::443                      :::*                        LISTEN      2218/httpd
tcp        0      0 :::80                       :::*                        LISTEN      2218/httpd
tcp        0      0 :::22                       :::*                        LISTEN      1051/sshd