Look for the process of listening on the specified port, for the system administrator, is an eternal topic. Historically, Linux distribution can use a third party lsof.
ddos@ubuntu:~$ sudo netstat -na -p tcp | grep LISTEN
tcp 0 0 127.0.1.1:53 0.0.0.0:* LISTEN 1312/dnsmasq
tcp 0 0 127.0.0.1:631 0.0.0.0:* LISTEN 849/cupsd
tcp6 0 0 :::80 :::* LISTEN 3906/apache2
tcp6 0 0 ::1:631 :::* LISTEN 849/cupsd
unix 2 [ ACC ] STREAM LISTENING 27711 2302/gnome-session- @/tmp/.ICE-unix/2302
unix 2 [ ACC ] STREAM LISTENING 25345 2065/gnome-keyring- /run/user/1000/keyring/ssh
unix 2 [ ACC ] STREAM LISTENING 24839 1643/dockerd /run/docker/libnetwork/ca7c82c70397ece4d65dc3d11e84bd9bb4074a00dc47d8986fc0936c7fc6424c.sock
unix 2 [ ACC ] STREAM LISTENING 26129 2402/pulseaudio /run/user/1000/pulse/native
unix 2 [ ACC ] STREAM LISTENING 17693 1/init /var/run/dbus/system_bus_socket
unix 2 [ ACC ] STREAM LISTENING 17696 1/init /run/snapd.socket
unix 2 [ ACC ] STREAM LISTENING 20195 1082/Xorg @/tmp/.X11-unix/X0
unix 2 [ ACC ] STREAM LISTENING 17698 1/init /run/snapd-snap.socket
unix 2 [ ACC ] STREAM LISTENING 17700 1/init /var/run/docker.sock
unix 2 [ ACC ] STREAM LISTENING 23846 1643/dockerd /var/run/docker/metrics.sock
unix 2 [ ACC ] STREAM LISTENING 17702 1/init /var/run/avahi-daemon/socket
unix 2 [ ACC ] STREAM LISTENING 20196 1082/Xorg /tmp/.X11-unix/X0
unix 2 [ ACC ] STREAM LISTENING 17705 1/init /var/run/cups/cups.sock
unix 2 [ ACC ] STREAM LISTENING 17708 1/init /run/uuidd/request
unix 2 [ ACC ] STREAM LISTENING 17711 1/init /run/acpid.socket
unix 2 [ ACC ] STREAM LISTENING 25889 2258/dbus-daemon @/tmp/dbus-A9cGjgEig1
unix 2 [ ACC ] STREAM LISTENING 25409 2217/ibus-daemon @/tmp/ibus/dbus-rlJqRPCj
unix 2 [ ACC ] STREAM LISTENING 25922 2276/gpg-agent /home/ddos/.gnupg/S.gpg-agent
unix 2 [ ACC ] STREAM LISTENING 22385 1673/docker-contain /var/run/docker/libcontainerd/docker-containerd.sock
unix 2 [ ACC ] STREAM LISTENING 25207 2059/systemd /run/user/1000/systemd/private
unix 2 [ ACC ] STREAM LISTENING 27712 2302/gnome-session- /tmp/.ICE-unix/2302
unix 2 [ ACC ] STREAM LISTENING 899 1/init /run/systemd/private
unix 2 [ ACC ] STREAM LISTENING 25220 2065/gnome-keyring- /run/user/1000/keyring/control
unix 2 [ ACC ] STREAM LISTENING 909 1/init /run/systemd/journal/stdout
unix 2 [ ACC ] SEQPACKET LISTENING 922 1/init /run/udev/control
unix 2 [ ACC ] STREAM LISTENING 25303 2155/dbus-daemon @/tmp/dbus-BkkYQfGN8Y
unix 2 [ ACC ] STREAM LISTENING 21158 898/NetworkManager /var/run/NetworkManager/private-dhcp
unix 2 [ ACC ] STREAM LISTENING 25259 2067/upstart @/com/ubuntu/upstart-session/1000/2067
unix 2 [ ACC ] STREAM LISTENING 980 1/init /run/systemd/fsck.progress
unix 2 [ ACC ] STREAM LISTENING 25342 2065/gnome-keyring- /run/user/1000/keyring/pkcs11
Now, you want to know which is listening on “tcp6 0 0 :::80 :::* LISTEN 3906/apache2 ”
sudo lsof -ni tcp:80
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
apache2 3906 root 4u IPv6 33083 0t0 TCP *:http (LISTEN)
apache2 3909 www-data 4u IPv6 33083 0t0 TCP *:http (LISTEN)
apache2 3910 www-data 4u IPv6 33083 0t0 TCP *:http (LISTEN)sudo ps -opid,ppid,uid,addr,fname,comm,args -p 3906
PID PPID UID ADDR COMMAND COMMAND COMMAND
3906 1 0 – apache2 apache2 /usr/sbin/apache2 -k start
sudo lsof -n -p 3906| grep TCP
apache2 3906 root 3u sock 0,8 0t0 33082 protocol: TCP
apache2 3906 root 4u IPv6 33083 0t0 TCP *:http (LISTEN)
