Linux who listen on port

How to know what program is listening on a given port?

I suspect a program is listening on port 8000 on my machine. When I run the following command, I get this error:

> python -m SimpleHTTPServer # Lots of python error socket.error: [Errno 98] Address already in use 

If I use another port ( 8000 is the default), the web server runs fine. If I run wget localhost:8000 from the command line, it returns 404 Not Found . What can I do (or what tools are available) to find what program is listening on port 8000 , and from there where that program is configured?

8 Answers 8

Open your terminal and type as

that command will list you the application used by that port with PID. (If no results run via sudo since your might have no permission to certain processes.)

For example, with port 8000 ( python3 -m http.server ):

$ lsof -i :8000 COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME python3 3269 user 3u IPv4 1783216 0t0 TCP *:8000 (LISTEN) 

$ sudo lsof -i :22 COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME sshd 998 root 3u IPv4 1442116 0t0 TCP *:ssh (LISTEN) sshd 998 root 4u IPv6 1442118 0t0 TCP *:ssh (LISTEN) 

@Imray the example searches for port 8881. The PID column contains the process IDs and the NAME column contains the ports.

You can use netstat to see which process is listening on which port.

You can use this command to have a full detail :

if you need to know exactly which one is listening on port 8000 you can use this :

sudo netstat -peanut | grep ":8000 " 

There is no process that can hide from netstat.

To kill/end the process use kill where is the process id displayed in the last column of netstat ‘s output. Eg. kill 31612 .

To expound on the answer by @33833 you can get some very detailed info, for example:

$ lsof -i :8000 COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME squid3 1289 proxy 15u IPv6 14810490 0t0 TCP *:8000 (LISTEN) $ ps -fp 1289 UID PID PPID C STIME TTY TIME CMD proxy 1289 1 0 09:48 ? 00:00:00 /usr/sbin/squid3 -N -f /etc/squid-deb-proxy/squid-deb-proxy.conf 

I can see right there that squid is the process, but it is actualy my squid-deb-proxy that is taking up the port.

Another good example of a java app:

$ lsof -i :4242 COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME java 3075 root 86u IPv4 12019 0t0 TCP *:4242 (LISTEN) $ ps -fp 3075 UID PID PPID C STIME TTY TIME CMD root 3075 1 15 May24 ? 3-16:07:25 /usr/local/crashplan/jre/bin/java -Dfile.encoding=UTF-8 -Dapp=CrashPlanService -DappBaseName=CrashPl 

You can see in lsof (LiSt Open Files) that it is java, which is less than helpful. Running the ps command with the PID we can see right away that it is CrashPlan.

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4 Ways to Find Out What Ports Are Listening in Linux

The state of a port is either open, filtered, closed, or unfiltered. A port is said to be open if an application on the target machine is listening for connections/packets on that port.

In this article, we will explain four ways to check open ports and also will show you how to find which application is listening on what port in Linux.

1. Using Netstat Command

Netstat is a widely used tool for querying information about the Linux networking subsystem. You can use it to print all open ports like this:

The flag -l tells netstat to print all listening sockets, -t shows all TCP connections, -u displays all UDP connections and -p enables printing of application/program name listening on the port.

To print numeric values rather than service names, add the -n flag.

You can also use grep command to find out which application is listening on a particular port, for example.

$ sudo netstat -lntup | grep "nginx"

Alternatively, you can specify the port and find the application bound to, as shown.

$ sudo netstat -lntup | grep ":80"

2. Using ss Command

ss command is another useful tool for displaying information about sockets. It’s output looks similar to that of netstat. The following command will show all listening ports for TCP and UDP connections in numeric value.

3. Using Nmap Command

Nmap is a powerful and popular network exploration tool and port scanner. To install nmap on your system, use your default package manager as shown.

$ sudo apt install nmap [On Debian/Ubuntu] $ sudo yum install nmap [On CentOS/RHEL] $ sudo dnf install nmap [On Fedora 22+]

To scan all open/listening ports in your Linux system, run the following command (which should take a long time to complete).

$ sudo nmap -n -PN -sT -sU -p- localhost

4. Using lsof Command

The final tool we will cover for querying open ports is lsof command, which is used to list open files in Linux. Since everything is a file in Unix/Linux, an open file may be a stream or a network file.

To list all Internet and network files, use the -i option. Note that this command shows a mix of service names and numeric ports.

To find which application is listening on a particular port, run lsof in this form.

That’s all! In this article, we have explained four ways to check open ports in Linux. We also showed how to check which processes are bound upon particular ports. You can share your thoughts or ask any questions via the feedback form below.

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3 Ways to Find Out Which Process Listening on a Particular Port

A port is a logical entity that represents an endpoint of communication and is associated with a given process or service in an operating system. In previous articles, we explained how to find out the list of all open ports in Linux and how to check if remote ports are reachable using the Netcat command.

In this short guide, we will show different ways of finding the process/service listening on a particular port in Linux.

1. Using netstat Command

netstat (network statistics) command is used to display information concerning network connections, routing tables, interface stats, and beyond. It is available on all Unix-like operating systems including Linux and also on Windows OS.

In case you do not have it installed by default, use the following command to install it.

$ sudo apt-get install net-tools [On Debian/Ubuntu & Mint] $ sudo dnf install net-tools [On CentOS/RHEL/Fedora and Rocky Linux/AlmaLinux] $ pacman -S netstat-nat [On Arch Linux] $ emerge sys-apps/net-tools [On Gentoo] $ sudo dnf install net-tools [On Fedora] $ sudo zypper install net-tools [On openSUSE]

Once installed, you can use it with the grep command to find the process or service listening on a particular port in Linux as follows (specify the port).

In the above command, the flags.

• l – tells netstat to only show listening sockets.
• t – tells it to display tcp connections.
• n – instructs it to show numerical addresses.
• p – enables showing of the process ID and the process name.
• grep -w – shows matching of exact string (:80).

Note: The netstat command is deprecated and replaced by the modern ss command in Linux.

2. Using lsof Command

lsof command (List Open Files) is used to list all open files on a Linux system.

To install it on your system, type the command below.

$ sudo apt-get install lsof [On Debian, Ubuntu and Mint] $ sudo yum install lsof [On RHEL/CentOS/Fedora and Rocky Linux/AlmaLinux] $ sudo emerge -a sys-apps/lsof [On Gentoo Linux] $ sudo pacman -S lsof [On Arch Linux] $ sudo zypper install lsof [On OpenSUSE]

To find the process/service listening on a particular port, type (specify the port).

3. Using fuser Command

fuser command shows the PIDs of processes using the specified files or file systems in Linux.

You can install it as follows:

$ sudo apt-get install psmisc [On Debian, Ubuntu and Mint] $ sudo yum install psmisc [On RHEL/CentOS/Fedora and Rocky Linux/AlmaLinux] $ sudo emerge -a sys-apps/psmisc [On Gentoo Linux] $ sudo pacman -S psmisc [On Arch Linux] $ sudo zypper install psmisc [On OpenSUSE]

You can find the process/service listening on a particular port by running the command below (specify the port).

Then find the process name using PID number with the ps command like so.

$ ps -p 2053 -o comm= $ ps -p 2381 -o comm=

You can also check out these useful guides about processes in Linux.

You might also like:

That’s all! Do you know of any other ways of finding the process/service listening on a particular port in Linux, let us know via the comment form below.

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Determine the process pid listening on a certain port

As the title says, I’m running multiple game servers, and every of them has the same name but different PID and the port number. I would like to match the PID of the server which is listening on certain port, and then I would like to kill this process. I need that in order to complete my bash script. Is that even possible? Because it didn’t find yet any solutions on the web.

8 Answers 8

Short version which you can pass to kill command:

This also includes processes that are connected on that port. lsof -i4TCP:80 -sTCP:LISTEN -t is probably what you want, instead.

Exactly what I was looking for. I wanted to kill a process by searching for the port it is running at.

@Nevir what do you mean by » also includes processes that are connected on that port»? Can you please explain?

The -p flag of netstat gives you PID of the process:

*use sudo if showing — instead of PID

Edit: The command that is needed to get PIDs of socket users in FreeBSD is sockstat . As we worked out during the discussion with @Cyclone, the line that does the job is:

sockstat -4 -l | grep :80 | awk '' | head -1 

netstat: 80: unknown or uninstrumented protocol used the 80 (nginx) port for testing purpoes. Not worked.

netstat -p -l | grep $PORT and lsof -i :$PORT solutions are good but I prefer fuser $PORT/tcp extension syntax to POSIX (which work for coreutils ) as with pipe:

it prints pure pid so you can drop sed magic out.

One thing that makes fuser my lover tools is ability to send signal to that process directly (this syntax is also extension to POSIX):

$ fuser -k $port/tcp # with SIGKILL $ fuser -k -15 $port/tcp # with SIGTERM $ fuser -k -TERM $port/tcp # with SIGTERM 

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