Netstat for Linux & window:

 

 for Linux

netstat -tunlp

The options used in this command have the following meaning:

• -t - Show TCP ports.
• -u - Show UDP ports.
• -n - Show numerical addresses instead of resolving hosts.
• -l - Show only listening ports.
• -p - Show the PID and name of the listener’s process. This information is shown only if you run the command as root or sudo user.

The output will look something like this:

Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name    
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      445/sshd            
tcp        0      0 0.0.0.0:25              0.0.0.0:*               LISTEN      929/master          
tcp6       0      0 :::3306                 :::*                    LISTEN      534/mysqld          
tcp6       0      0 :::80                   :::*                    LISTEN      515/apache2         
tcp6       0      0 :::22                   :::*                    LISTEN      445/sshd            
tcp6       0      0 :::25                   :::*                    LISTEN      929/master          
tcp6       0      0 :::33060                :::*                    LISTEN      534/mysqld          
udp        0      0 0.0.0.0:68              0.0.0.0:*            

 

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Option #1: lsof command

The syntax is:
$ sudo lsof -i -P -n
$ sudo lsof -i -P -n | grep LISTEN
$ doas lsof -i -P -n | grep LISTEN ### [OpenBSD] ###
Sample outputs:

Fig.01: Check the listening ports and applications with lsof command

 

==========================

To get a list of all listening TCP ports with lsof type:

sudo lsof -nP -iTCP -sTCP:LISTEN

The options used are as follows:

• -n - Do not convert port numbers to port names.
• -p - Do not resolve hostnames, show numerical addresses.
• -iTCP -sTCP:LISTEN - Show only network files with TCP state LISTEN.

COMMAND   PID     USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
sshd      445     root    3u  IPv4  16434      0t0  TCP *:22 (LISTEN)
sshd      445     root    4u  IPv6  16445      0t0  TCP *:22 (LISTEN)
apache2   515     root    4u  IPv6  16590      0t0  TCP *:80 (LISTEN)
mysqld    534    mysql   30u  IPv6  17636      0t0  TCP *:3306 (LISTEN)
mysqld    534    mysql   33u  IPv6  19973      0t0  TCP *:33060 (LISTEN)
apache2   764 www-data    4u  IPv6  16590      0t0  TCP *:80 (LISTEN)
apache2   765 www-data    4u  IPv6  16590      0t0  TCP *:80 (LISTEN)
master    929     root   13u  IPv4  19637      0t0  TCP *:25 (LISTEN)
master    929     root   14u  IPv6  19638      0t0  TCP *:25 (LISTEN)

For Windows:

netstat -a -b