I would like to see what ports are open on my machine, e.g. what ports my machine is listening on. E.g. port 80 if I have installed a web server, and so on.
Is there any command for this?
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Nmap ("Network Mapper") is a free and open source utility for network exploration or security auditing
nmap 192.168.1.33 internal Pc or
nmap external ip address
I've always used this:
sudo netstat -ntlp | grep LISTEN
Other good ways to find out what ports are listenting and what your firewall rules are:
sudo netstat -tulpn
sudo ufw status
To list open ports use the
$ sudo netstat -tulpn | grep LISTEN tcp 0 0 127.0.0.1:53 0.0.0.0:* LISTEN 5452/dnsmasq tcp 0 0 127.0.0.1:631 0.0.0.0:* LISTEN 1037/cupsd tcp6 0 0 ::1:631 :::* LISTEN 1037/cupsd
In the above example three services are bound to the loopback address.
IPv4 services bound to the loopback address "127.0.0.1" are only available on the local machine. The equivalent loopback address for IPv6 is "::1". The IPv4 address "0.0.0.0" means "any IP address", which would mean that other machines could potentially connect to any of the locally configured network interfaces on the specific port.
Another method is to use the
$ sudo lsof -nP -i | grep LISTEN cupsd 1037 root 9u IPv6 11276 0t0 TCP [::1]:631 (LISTEN) cupsd 1037 root 10u IPv4 11277 0t0 TCP 127.0.0.1:631 (LISTEN) dnsmasq 5452 nobody 5u IPv4 212707 0t0 TCP 127.0.0.1:53 (LISTEN)
For more details see
man netstat or
This is enough to show that there is a process listening on IP address
0.0.0.0 (needed so it will reply to any request) on port 80 (standard web server port number). In my case this shows it is the web server
$ sudo netstat -ntlp | grep :80 tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN 2495/lighttpd
If you later want to make sure that the only thing you allow through your firewall is port 80 I often use ShieldsUp from www.grc.com to perform a firewall test.
sudo iptables -L will list the port rules for your pc.
Note that if you are using ufw or shorewall firewalls the output maybe be hard to read.
In that case rather use
sudo ufw status for example.
This is not very useful on its own as even if a port is open access will still be denied if there is no process listening on that port.
If you are looking for continuous monitoring of ports for server machines or local I think you can also use graphical version of nmap i.e Zenmap for more detailed version
Zenmap is the official graphical user interface (GUI) for the Nmap Security Scanner.
Supports available (Linux, Windows, Mac OS X, BSD, etc.)
Have a look to this tool view: