"The hostname, if not specified or specified as '' or 'localhost', will default to a MySQL server running on the local machine using the default for the UNIX socket. To connect to a MySQL server on the local machine via TCP, you must specify the loopback IP address (127.0.0.1) as the host."

"To connect to a MySQL server on localhost using TCP/IP, you must specify the hostname as 127.0.0.1 (with the optional port)."