Error binding socket to :::25, status = EADDRINUSE (Solved)

Centos 

$ yum install net-tools 

Fedora: 

$ sudo dnf install net-tools 

Debian, Ubuntu: 

$ sudo apt install net-tools

netstat -tulpn

netstat -tulpn | grep -w 2500

Result: tcp     0         0 0.0.0.0:2500             0.0.0.0:*

kill 942