How to check if a port is open in Linux?

In Linux, we can check whether the port is open by using the lsof command and netstat command on the command line.

Method 1: Use the lsof command

We can use the lsof command to check whether a certain port Open, the basic syntax is as follows:

lsof -i:端口号

If there is no output, it means that the port number is not open

The following figure takes port 80 and port 53 as an example to check whether port 80 and port 53 are open

You can also use the lsof -i command to directly output the open ports to check whether certain ports are open.

Method 2: Use the netstat command

The netstat command can provide network-related information about the host.

We can use netstat -atu to check open ports in linux

Netstat flags we use: -a, -t and -u Introduction

-a: All sockets.

-t: TCP connection of the program

-u: UDP connection of the program

You can also add the -p flag to display the related PID of the process or program name.

To display only UDP ports, you can use the following command:

To display only TCP ports, you can use the following Command:

Related video tutorial recommendation: "Linux Tutorial"

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