I’ve installed MAMP on my Mac to do some changes to my blog. I tried to set the WordPress wp-config.php file to connect to localhost:8889, but got an error that It could not connect to the database. After replacing localhost:8889 to 127.0.0.1:8889 it works. My quick guess is that permissions for the root user is set to allow connections 127.0.0.1, but not localhost. Anyway, it works now.
My wp-config.php file looks like this:
define('DB_NAME', 'wordpress'); /** MySQL database username */ define('DB_USER', 'root'); /** MySQL database password */ define('DB_PASSWORD', 'root'); /** MySQL hostname */ define('DB_HOST', '127.0.0.1:8889');