View listen ports linux

How can I see what ports are open on my machine?

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?

10 Answers 10

If the netstat command is not available, install it with:

sudo apt install net-tools 

-l already filters for listening. grep LISTEN won’t help beyond hiding 2 lines of header information.

-t : tcp, -l : listening socket, -p : show pid and program name, -n : print 127.0.0.1:80 instead of localhost:http . Reference: linux.die.net/man/8/netstat

The expanded command is sudo netstat —tcp —listening —programs —numeric . There’s no need to use grep unless you want to eliminate column headers.

nmap (install)

Nmap («Network Mapper») is a free and open source utility for network exploration or security auditing.

Use nmap 192.168.1.33 for internal PC or nmap external IP address .

More information man nmap .

Zenmap is the official GUI frontend.

Remember that there is a difference between nmap localhost and nmap 192.168.0.3 (or what ever you machine IP is)

I think netstat is a better answer to this. netstat will list what the system is listening on directly, and without using an additional application or doing unnecessary calls over localhost or thought the network.

This is stupid. If you have access to the computer, just use netstat -ln . You’ll instantly see all the open ports.

nmap localhost didn’t find services that were bound only to localhost. For example, I run influxd with bind-address:localhost:8086 . That didn’t show up in sudo nmap localhost , but did show up in sudo netstat -tulpn .

Other good ways to find out what ports are listenting and what your firewall rules are:

To list open ports use the netstat command.

 $ 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 lsof command:

 $ 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 man lsof .

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Check for Listening Ports in Linux

When troubleshooting network connectivity or application-specific issues, one of the first things to check should be what ports are actually in use on your system and which application is listening on a specific port.

This article explains how to use the netstat , ss and lsof commands to find out which services are listening on which ports. The instructions are applicable for all Linux and Unix-based operating systems like macOS.

What is Listening Port

Network port is identified by its number, the associated IP address, and type of the communication protocol, such as TCP or UDP.

Listening port is a network port on which an application or process listens on, acting as a communication endpoint.

Each listening port can be open or closed (filtered) using a firewall. In general terms, an open port is a network port that accepts incoming packets from remote locations.

You can’t have two services listening to the same port on the same IP address.

For example, if you are running an Apache web server that listens on ports 80 and 443 and you try to install Nginx , the later will fail to start because the HTTP and HTTPS ports are already in use.

Check Listening Ports with netstat

netstat is a command-line tool that can provide information about network connections.

To list all TCP or UDP ports that are being listened on, including the services using the ports and the socket status use the following command:

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:* 966/dhclient 

The important columns in our case are:

• Proto — The protocol used by the socket.
• Local Address — The IP Address and port number on which the process listen to.
• PID/Program name — The PID and the name of the process.

If you want to filter the results, use the grep command . For example, to find what process listens on TCP port 22 you would type:

sudo netstat -tnlp | grep :22 

The output shows that on this machine port 22 is used by the SSH server:

tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 445/sshd tcp6 0 0 . 22 . * LISTEN 445/sshd 

If the output is empty it means that nothing is listening on the port.

You can also filter the list based on criteria, for example, PID, protocol, state, and so on.

netstat is obsolete and replaced with ss and ip , but still it is of the most used commands to check network connections.

Check Listening Ports with ss

ss is the new netstat . It lacks some of the netstat features, but exposes more TCP states and it is slightly faster. The command options are mostly the same, so the transition from netstat to ss is not difficult.

To get a list of all listening ports with ss you would type:

The output is almost the same as the one reported by netstat :

State Recv-Q Send-Q Local Address:Port Peer Address:Port LISTEN 0 128 0.0.0.0:22 0.0.0.0:* users:(("sshd",pid=445,fd=3)) LISTEN 0 100 0.0.0.0:25 0.0.0.0:* users:(("master",pid=929,fd=13)) LISTEN 0 128 *:3306 *:* users:(("mysqld",pid=534,fd=30)) LISTEN 0 128 *:80 *:* users:(("apache2",pid=765,fd=4),("apache2",pid=764,fd=4),("apache2",pid=515,fd=4)) LISTEN 0 128 [::]:22 [::]:* users:(("sshd",pid=445,fd=4)) LISTEN 0 100 [::]:25 [::]:* users:(("master",pid=929,fd=14)) LISTEN 0 70 *:33060 *:* users:(("mysqld",pid=534,fd=33)) 

Check Listening Ports with lsof

lsof is a powerful command-line utility that provides information about files opened by processes.

In Linux, everything is a file. You can think of a socket as a file that writes to the network.

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) 

Most of the output columns names are self-explanatory:

• COMMAND , PID , USER — The name, the pid and the user running the program associated with the port.
• NAME — The port number.

To find what process is listening on a particular port, for example, port 3306 you would use:

sudo lsof -nP -iTCP:3306 -sTCP:LISTEN 

The output shows that MySQL server uses port 3306 :

COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME mysqld 534 mysql 30u IPv6 17636 0t0 TCP *:3306 (LISTEN) 

For more information, visit the lsof man page and read about all other powerful options of this tool.

Conclusion

We have shown you several commands that you can use to check what ports are in use on your system, and how to find what process listens on a specific port.

If you have any questions or remarks, please leave a comment below.

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How to Find All Open Ports (Listening Ports) on Ubuntu Linux

This brief tutorial shows students and new users how to find all ports in use or listening ports when using Ubuntu Linux systems.

The steps below should be handy if you’re a server administrator or web admin and want to ensure that only approved ports are opened on your Ubuntu Linux server.

Most servers built for public access will have services that listen to their assigned ports for communication. In some cases, ports that are not in use will stay open, which may lead to them being exploited.

Ubuntu comes with some default commands that can be used to scan your servers for open ports. The steps below will show you how to use some of these commands to identify listening ports and how to find them.

Since you can’t have two services listening on the same port, it’s a good chance that you may have ports you’re probably not using, and you’ll want to close them.

A network port is identified by its number, the associated IP address, and the type of communication protocol, such as TCP or UDP.

To identify listening ports on Ubuntu, follow the steps below:

Use the netstat Command

netstat is a command-line tool that can provide information about network connections, including IP addresses, ports, and services communicating on these ports.

If you don’t already netstat tool installed, use the commands below to install it.

sudo apt install net-tools

If you want to list all ports available on a server, you run the commands below:

For detailed command options, view the bullet below:

• -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.

When you run the Command above with the options, you should see similar lines as below:

Active Internet connections (only servers) Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name tcp 0 0 127.0.0.53:53 0.0.0.0:* LISTEN 486/systemd-resolve tcp 0 0 127.0.0.1:631 0.0.0.0:* LISTEN 2851/cupsd

That should give you a lot of information.

However, if you only want to see a specific service name or port, you can use the netstat Command with the option above with grep.

The example below shows you to scan for open ports and only list port 22.

sudo netstat -tnlp | grep :22

You should see a similar line below:

tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 25538/sshd tcp6 0 0 . 22 . * LISTEN 25538/sshd

The Command above using grep shows port 22 only, and sshd service is listening on that port.

Use the ss Command

netstat is not installed on Ubuntu by default. The ss command is installed as a replacement for netstat. As with netstat, the ss command displays network information on Linux systems.

netstat and ss commands share almost the same command options. So if you’re used to netstat, the ss command should work almost the same.

To view all listening ports on Ubuntu using the ss command, run the Command below:

You should see a similar screen as shown below:

NetidState Recv-Q Send-Q Local Address:Port Peer Address:Port udp UNCONN 0 0 127.0.0.53%lo:53 0.0.0.0:* users:(("systemd-resolve",pid=486,fd=12)) udp UNCONN 0 0 0.0.0.0:68 0.0.0.0:* users:(("dhclient",pid=782,fd=6)) tcp LISTEN 0 5 [::1]:631 [::]:* users:(("cupsd",pid=2851,fd=6))

The output above is similar to the netstat Command we ran previously.

Use the lsof Command

The lsof Command is another powerful utility available to Linux systems that allows you to display networking information.

To list all listening TCP ports using the lsof Command, run it with the options below:

sudo lsof -nP -iTCP -sTCP:LISTEN

You should see similar lines as shown below:

COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME systemd-r 486 systemd-resolve 13u IPv4 15733 0t0 TCP 127.0.0.53:53 (LISTEN) cupsd 2851 root 6u IPv6 36958 0t0 TCP [::1]:631 (LISTEN) cupsd 2851 root 7u IPv4 36959 0t0 TCP 127.0.0.1:631 (LISTEN) sshd 25538 root 3u IPv4 77978 0t0 TCP *:22 (LISTEN) sshd 25538 root 4u IPv6 77980 0t0 TCP *:22 (LISTEN)

That should list open ports as well.

Now you know how to list listing ports on Ubuntu; you can use any of the commands above to find ports that are not in use and turn off services to them.

Richard W

I love computers; maybe way too much. What I learned I try to share at geekrewind.com.

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