Linux which ports are in use

Since everything on a Linux system can be considered a file, the lsof tool can report on many aspects of a system, including open network interfaces and network connections. The lsof tool is preinstalled on many Linux distributions, so you may consider using it before a tool you need to install. This mode allows you to run the lsof command continuously on a timed interval.

When inspecting your system to find information about which ports are in use, lsof can return information about which user and processes are using a specific port. For example, when working with a local development environment you may want to find which localhost ports are currently in use.

Use the following command to retrieve this information:. To learn more about the lsof command read our How to List Open Files with lsof guide. This guide provides information about command-line options, the anatomy of the lsof output, and filtering your output with regular expressions. This page was originally published on Thursday, February 25, Let us know if this guide made it easy to get the answer you needed.

A topic that contains an answer also for kernel level services and programs serverfault. Add a comment. Active Oldest Votes. Improve this answer. GNU netstat knows the parameters -t , -u , -p , -l , -e , and -n. Thanks to the options parser it can be expressed as -tuplen.

Also, the telnet command usually does only supports TCP, so you're out of luck if the service you want to check runs on another protocol. It supports UDP too. When I go to the netstat man page it says netstat is obsolete. Show 5 more comments. Adrian Macneil Adrian Macneil 1, 2 2 gold badges 11 11 silver badges 11 11 bronze badges. Written above: if you get a time out or deny, the port is not open — Industrial.

What if you don't have perms to install telnet? Is there another standard tool? But I can ssh into that machine. Show 3 more comments. In that case, run: iptables -L -n This will show all the firewall rules as defined on your system. Could you pls add how to undo the iptables -I command? Basically, look up the documentation.

I'd highly recommend using ufw just apt install ufw then see man ufw it's a more user-friendly frontend for iptables. DheerajThedijje - then that port isn't open — warren.

Yes it was not, got it. Create a free Team What is Teams? Learn more. Asked 8 years, 10 months ago. Active 2 months ago. Viewed k times. Improve this question. Wilfred Hughes 2 2 silver badges 7 7 bronze badges. Stanley Mungai Stanley Mungai 2, 3 3 gold badges 11 11 silver badges 8 8 bronze badges.

Add a comment. Active Oldest Votes. Improve this answer. Bojangles 1 1 gold badge 8 8 silver badges 18 18 bronze badges. Note that netstat is deprecated on many systems and ss should be used instead. Since net-tools is deprecated , you can use the ss command instead of netstat if netstat is not present on your machine: ss -lntu should work similarly to netstat -lntu according to the built-in help: -n, --numeric don't resolve service names -l, --listening display listening sockets -t, --tcp display only TCP sockets -u, --udp display only UDP sockets -p, --processes show process using socket.

Mustafa 4 4 bronze badges. The command lsof is the most basic of how many we lend you and, being a native of Linux, the base that every user should know. To know the ports open in the system through this command, you must enter a sequence like the following, which it will show you various information where we will highlight: the name of the application for example, sshd , the socket of the program in this case the IP address The command netstat varies slightly in its syntax with respect to the previous one but presents some parameters much easier to memorize thanks to a simple mnemonic word.

From now on do not forget the word slut , which refers to the following characteristics:. Thus, entering the command and filtering it with a pipe we can get information about a certain port. Nmap It is a utility that we allows to perform a multitude of scans in our system and one of them, the one of open ports in the equipment.

Take a look at the following example. With these three applications you already have enough tools to determine the open ports of your machine. Do you use the same tools or do you know any other way to verify the open ports of a system? The content of the article adheres to our principles of editorial ethics.