Yes, the authentication server needs to be online all the time.
Sending usernames and passwords in plaintext is poor security: you would want to put them through a one-way hash first so no one could sniff them (or use a secure connection.)
MySQL is one of the better free SQL servers, and there are plenty of tutorials on how to set it up.
Sending usernames and passwords in plaintext is poor security: you would want to put them through a one-way hash first so no one could sniff them (or use a secure connection.)
MySQL is one of the better free SQL servers, and there are plenty of tutorials on how to set it up.