How to query the port number in linux

Method: 1. Use lsof to query the port number. lsof is a tool that lists open files in the current system. The syntax is "lsof -i:port number"; 2. Use the netstat command to query the port number. The syntax is "netstat -tunlp | grep port number".

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

How to query the port number in Linux

Linux can use the lsof and netstat commands to check the port occupancy.

lsof

lsof (list open files) is a tool that lists open files on the current system.

lsof Check the port occupancy syntax format:

lsof -i:端口号

Example

Check the server 8000 port occupancy:

# lsof -i:8000 COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME nodejs 26993 root 10u IPv4 37999514 0t0 TCP *:8000 (LISTEN)

You can see that the 8000 port has been lightly used nodejs service occupied.

lsof -i requires root user permissions to execute, as shown below:

More lsof commands are as follows:

lsof - i:8080: Check the 8080 port occupation

lsof abc.txt: Display the process that opens the file abc.txt

lsof -c abc: Display the file currently opened by the abc process

lsof -c -p 1234: List the files opened by the process with process number 1234

lsof -g gid: Display the status of the process belonging to gid

lsof d /usr/local/ : Display the files opened by the process in the directory

lsof D /usr/local/: Same as above, but the directory under the directory will be searched, which takes a longer time

lsof -d 4: Display using fd Process for 4

lsof -i -U: Display all open ports and UNIX domain files

netstat

netstat -tunlp is used to display Tcp, udp ports and processes and other related information.

netstat View port occupancy Syntax format:

netstat -tunlp | grep 端口号

• -t (tcp) Only display tcp related options

• -u (udp) Only display udp related options

• -n Refuse to display aliases, convert all numbers that can be displayed into numbers

• -l List only Out of the service status of Listen (monitoring)

• -p Display the name of the program that establishes the relevant link

For example, to view the situation of port 8000, use The following commands:

# netstat -tunlp | grep 8000 tcp 0 0 0.0.0.0:8000 0.0.0.0:* LISTEN 26993/nodejs

More commands:

netstat -ntlp //查看当前所有tcp端口 netstat -ntulp | grep 80 //查看所有80端口使用情况 netstat -ntulp | grep 3306 //查看所有3306端口使用情况

kill

After checking the process occupying the port, if you want to kill the corresponding The process can use the kill command:

kill -9 PID

As shown in the above example, we see that the PID corresponding to the 8000 port is 26993. Use the following command to kill the process:

kill -9 26993

Related recommendations: "Linux Video Tutorial》

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