How to Check If a Port is In Use on Linux

Method 1: Use lsof

sudo lsof -i -P -n
sudo lsof -i -P -n | grep LISTEN

sudo lsof -i:<portnumber>

Method 2: Use netstat

netstat -tulpn | grep LISTEN

sudo ss -tulw
sudo ss -tulwn

• -t - show TCP sockets
• -u - show UDP sockets
• -l - show listening sockets
• -p : show process name that opened sockets
• -n : do not use DNS

Method 3: Use nmap

sudo nmap -sTU -O