Four Methods for querying whether a port is occupied in Linux and four methods for linux

Four Methods for querying whether a port is occupied in Linux and four methods for linux

One interview question uses three different methods to check which process occupies 8080. The familiar methods are netstat and lsof, but what else can be done.

1. netstat or ss Command

netstat -anlp | grep 80

2. lsof command

This command is used to view the files occupied by the process.

lsof -i:80

3. fuser command

The fuser command is the opposite of the lsof command to check which process occupies a file. In Linux, everything is a file, so you can view common files, socket files, and file systems. The socket file contains the port number. For example, check port 22.

fuser 22/tcp -v                     USER        PID ACCESS COMMAND22/tcp:              root       1329 F.... sshd                     root       1606 f.... sshd

4. nmap Tool

Nmap always scans ports by default. It is very convenient to scan local ports.

nmap localhostStarting Nmap 5.51 ( http://nmap.org ) at 2018-03-03 18:00 CSTNmap scan report for localhost (127.0.0.1)Host is up (0.0000020s latency).Other addresses for localhost (not scanned): 127.0.0.1Not shown: 998 closed portsPORT   STATE SERVICE22/tcp open  ssh25/tcp open  smtpNmap done: 1 IP address (1 host up) scanned in 0.06 seconds

 

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