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How to check if a port is open in Linux

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Release: 2023-01-04 09:38:20
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Linux method to check whether the port is open: first open the port and switch to root user login; then use the [lsof -i:] port number command line; finally use the [netstat -aptn] command line to view all open The port number.

How to check if a port is open in Linux

The operating environment of this tutorial: linux7.3 system, DELL G3 computer

Linux method to check whether the port is open:

1. First, we open the Linux command operation interface to view the port, as shown in the figure

How to check if a port is open in Linux

2. Then in order to obtain higher Permissions (view all ports), switch to root user login here

How to check if a port is open in Linux

3. The first method is to use the lsof -i:port number command line, taking 80 as an example , as shown in the figure

How to check if a port is open in Linux

#4. If there is no output, it means that the port number is not opened. In order to facilitate testing, I will detect an open port number here, and it will output The information shown in the figure

How to check if a port is open in Linux

5. The second method is to use the netstat -aptn command line to view all open port numbers,

How to check if a port is open in Linux

6. The command shown in the figure is to view all port numbers using the udp protocol in the system.

How to check if a port is open in Linux

7. Then this command is to view the system Use the port number information of the tcp protocol

How to check if a port is open in Linux

8. Finally, there is a client test method, which is to use the Telnet ip port number command, but I am in the virtual machine Linux The test was not successful. The test was successful on the remote Linux system. I don’t know what happened.

Related learning recommendations: linux video tutorial

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