You should also check that your MySQL server has been configured to accept remote TCP connections.
In your MySQL configuration file (my.cnf), you need the following at least:
port = 3306 # Port MySQL listens on
bind-address = 192.168.1.15 # IP address of your server
# skip-networking # This should be commented out to enable networking
The default in some configurations is for the bind-address to be 127.0.0.1, or to skip networking completely, which means only local or unix socket connections are possible. This is for security reasons.
You can also configure the bind-address to be 0.0.0.0 which means it will bind on all IP addresses on the server.
And lastly, check your firewall configuration to allow port 3306.