Mysql enable remote connection in centos,my.cnf does not have bind-address to comment out
The MySQL server listens on a single network socket for TCP/IP connections. This socket is bound to a single address, but it is possible for an address to map onto multiple network interfaces. The default address is 0.0.0.0. 


If the address is 0.0.0.0, the server accepts TCP/IP connections on all server host IPv4 interfaces. 
If the address is ::, the server accepts TCP/IP connections on all server host IPv4 and IPv6 interfaces. Use this address to permit both IPv4 and IPv6 connections on all server interfaces.


Source: http://dev.mysql.com/doc/refman/5.5/en/server-options.html#option_mysqld_bind-address

You can check your current bind address by executing:

$ mysql -b -e "SHOW GLOBAL VARIABLES like 'bind_address'"
+---------------+-----------+
| Variable_name | Value     |
+---------------+-----------+
| bind_address  | 127.0.0.1 |
+---------------+-----------+


on the command line, or SHOW GLOBAL VARIABLES like 'bind_address'; on a mysql client.