Find Out What Is Using TCP Port 80 in Linux

Use /proc/$pid/exec file find out what is using port 80

First, find out the processes PID that opened tcp port 90, enter:

# fuser 80/tcp

Sample outputs:

80/tcp:              12161 21776 25250 25393

Finally, find out process name associated with PID # 3813, enter:

# ls -l /proc/12161/exe

Sample outputs:

lrwxrwxrwx. 1 root root 0 Aug  9 17:08 /proc/12161/exe -> /usr/sbin/light