CD Key Server SDK Functions
| gcd_authenticate_user | Sends an authentication request. |
| gcd_disconnect_all | Calls gcd_disconnect_user for each user still online. |
| gcd_disconnect_user | Notify the validation server that a user has disconnected. |
| gcd_getkeyhash | Returns the key hash for the given user. |
| gcd_init | Initializes the Server API and creates the sockets and structures. |
| gcd_init_qr2 | Initializes the Server API and integrates the networking of the CDKey SDK with the Query & Reporting 2 SDK. |
| gcd_process_reauth | Used to respond to a reauthentication request made by the validation server proving the client is still on. |
| gcd_shutdown | Release the socket and send disconnect messages to the validation server for any clients still on the server. |
| gcd_think | Processes any pending data from the validation server and calls the callback to indicate whether a client was authorized or not. |