Q:

Explaining output of netstat -lntu

When I do netstat -lntu on a server running my web application, I get the list of services running on the system. I originally did this to see which ports were open. 
The list I see is given below. Can you tell me why 0.0.0.0:80 and 0.0.0.0:443 are replicated multiple times in this list? My webserver is nginx, and I'm running 16 worker processes (in case this is related to that).
Proto Recv-Q Send-Q Local Address           Foreign Address         State      
tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:5432            0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:443             0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:443             0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:443             0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:443             0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:443             0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:443             0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:443             0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:443             0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:443             0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:443             0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:443             0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:443             0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:443             0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:443             0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:443             0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:443             0.0.0.0:*               LISTEN     
tcp        0      0 0.0.0.0:6432            0.0.0.0:*               LISTEN     
tcp6       0      0 :::22                   :::*                    LISTEN     
tcp6       0      0 :::5432                 :::*                    LISTEN     
tcp6       0      0 :::443                  :::*                    LISTEN     
tcp6       0      0 :::443                  :::*                    LISTEN     
tcp6       0      0 :::443                  :::*                    LISTEN     
tcp6       0      0 :::443                  :::*                    LISTEN     
tcp6       0      0 :::443                  :::*                    LISTEN     
tcp6       0      0 :::443                  :::*                    LISTEN     
tcp6       0      0 :::443                  :::*                    LISTEN     
tcp6       0      0 :::443                  :::*                    LISTEN     
tcp6       0      0 :::443                  :::*                    LISTEN     
tcp6       0      0 :::443                  :::*                    LISTEN     
tcp6       0      0 :::443                  :::*                    LISTEN     
tcp6       0      0 :::443                  :::*                    LISTEN     
tcp6       0      0 :::443                  :::*                    LISTEN     
tcp6       0      0 :::443                  :::*                    LISTEN     
tcp6       0      0 :::443                  :::*                    LISTEN     
tcp6       0      0 :::443                  :::*                    LISTEN     
tcp6       0      0 :::6432                 :::*                    LISTEN     
udp        0      0 0.0.0.0:68              0.0.0.0:*                          
udp        0      0 0.0.0.0:6245            0.0.0.0:*                          
udp6       0      0 :::42854                :::* 

A:

Each entry represents one instance of a process listening on a socket. Specifically you have 16 processes running on your web server therefore you are seeing 16 on both the secure and the non secure listeners.

