MySQL - Can not connect to the database

Error message:

ERROR 2003 (HY000): Can't connect to MySQL server on '....' (111).

Solution:

1. Check connection details:
1. Verify that the IP is correct.
2. Verify that the Port number is correct.
3. Check username and password.
2. Network issues:
1. Check that connection to VPN or any other connection types.
2. Check Firewall definition.
3. For cloud instances: check that your IP is allowed.
3. Check that MySQL is up:
1. Check that the MySQL service is up:
1. Windows: in the services.
2. Linux: sudo systemctl start <SERVICENAME>
4. MySQL configurations:
1. Max connections - see here: http://copypastenet.blogspot.com/2021/02/mysql-see-orand-change-how-many.html 
2. cnf file configurations.