Linux: Netstat Command Examples

Netstat command displays various network related information such as network connections, routing tables, interface statistics, masquerade connections, multicast memberships etc.

List All Ports (both listening and non listening ports)
#netstat -a

root@localhost:~# netstat -a | more
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address Foreign Address State
tcp 0 0 *:mysql *:* LISTEN
tcp 0 0 *:http *:* LISTEN
tcp 0 0 *:ftp *:* LISTEN
tcp 0 0 *:ssh *:* LISTEN
udp 0 0 *:openvpn *:*

Active UNIX domain sockets (servers and established)
Proto RefCnt Flags Type State I-Node Path
unix 2 [ ACC ] STREAM LISTENING 8963 /var/run/dbus/system_bus_socket
unix 2 [ ACC ] STREAM LISTENING 9988 /var/run/mysqld/mysqld.sock
unix 2 [ ACC ] STREAM LISTENING 10048 private/proxymap

List all tcp ports
#netstat -at

root@localhost:~# netstat -at
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address Foreign Address State
tcp 0 0 *:mysql *:* LISTEN
tcp 0 0 *:http *:* LISTEN
tcp 0 0 *:ftp *:* LISTEN
tcp 0 0 *:ssh *:* LISTEN

Find out on which port a program is running
#netstat -ap

root@localhost:~# netstat -ap | grep http
tcp 0 0 *:http *:* LISTEN 1050/apache2
tcp 0 0 192.168.50.11:http 192.168.18.1:51615 TIME_WAIT -
tcp 0 0 192.168.50.11:http 192.168.18.1:51620 TIME_WAIT -
tcp 0 0 192.168.50.11:http 192.168.18.1:51614 TIME_WAIT -

Find more on netstat manual.