How to check programs and listening ports in Linux

Checking method: 1. Use the lsof command to check, the syntax is "sudo lsof -i -P -n | grep LISTEN" or "doas lsof -i -P -n | grep LISTEN"; 2. Use the netstat command To check the listening port and program, the syntax is "netstat -tulpn | grep LISTEN"; 3. Use the nmap command to check, the syntax is "sudo nmap -sT -O localhost".

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

How to check the programs and listening ports in Linux

1. Open a terminal, such as a shell command window.

2. Run any of the following commands:

sudo lsof -i -P -n | grep LISTEN
sudo netstat -tulpn | grep LISTEN
sudo nmap -sTU -O IP地址

Method 1: lsof command

The syntax is as follows:

$ sudo lsof -i -P -n
$ sudo lsof -i -P -n | grep LISTEN
$ doas lsof -i -P -n | grep LISTEN  ### OpenBSD

The output is as follows :

Look carefully at the last line of the above output:

sshd    85379     root    3u  IPv4 0xffff80000039e000      0t0  TCP 10.86.128.138:22 (LISTEN)

• sshd is a program The name

• 10.86.128.138 is the IP address of the sshd program binding (LISTEN)

• 22 is the TCP port being used (LISTEN)

• ##85379 is the process ID (PID) of the sshd task

Method 2: netstat command

You can use netstat as shown below to check the listening ports and programs.

Netstat syntax in Linux

$ netstat -tulpn | grep LISTEN

netstat syntax in FreeBSD/MacOS X

$ netstat -anp tcp | grep LISTEN
$ netstat -anp udp | grep LISTEN

netstat syntax in OpenBSD

$ netstat -na -f inet | grep LISTEN
$ netstat -nat | grep LISTEN

This command can also be used in windows ：

netstat -bano | more
netstat -bano | grep LISTENING
netstat -bano | findstr /R /C:"[LISTING]"

Method 3: nmap command

The syntax is as follows:

$ sudo nmap -sT -O localhost
$ sudo nmap -sU -O 192.168.2.13 ### 列出打开的 UDP 端口
$ sudo nmap -sT -O 192.168.2.13 ### 列出打开的 TCP 端口

The sample output is as follows:

You can merge TCP/UDP scanning with one command:

$ sudo nmap -sTU -O 192.168.2.13

Related recommendations: "

Linux Video Tutorial"

The above is the detailed content of How to check programs and listening ports in Linux. For more information, please follow other related articles on the PHP Chinese website!