When you install MySQL, only local access is enabled by default. Remote access is restricted in 2 ways:
In the config file /etc/mysql/my.cnf
Comment out the bind-address line:
#bind-address = 127.0.0.1
To enable the ruser from anywhere, you must use the grant command:
mysql> GRANT ALL PRIVILEGES ON *.* TO 'USERNAME'@'%' IDENTIFIED BY 'PASSWORD' WITH GRANT OPTION;
Replacing 'USERNAME' and password 'PASSWORD' with your own values of course.
After modifying the config file, you must restart the mysql service:
$ service mysql restart
Don't forget to use "sudo" (or su) if you're not logged in as root.