The address may be the problem. The C API recognizes special addresses like this and can interpret them oddly. Try "localhost" instead.

By the way, this isn't the best way to handle MySQL++ errors. In this instance, what perror appends to your string will only be correct if the connection failure is due to an error return from a system call. If something else goes wrong, such as the server rejecting your login parameters, it will tell you something like "no error" because the last system call to run probably succeeded.

Far better is to either a) enable exceptions, getting the error message from the exception object; or b) call either Query::error() or Connection::error() (same thing) to get the error message.