Messages sent to Buddies using this request are similar to the standard private messages (see the PrivateMessageRequest class), but they are specifically designed for the Buddy List System: they don't require a target Room, nor they require that involved Users are joined in a Room. Additionally, messages to Buddies are subject to specific validation, such as making sure that the recipient is in the sender's Buddy List and that the sender is not blocked by the recipient.
If the operation is successful, a SFSBuddyEvent.BUDDY_MESSAGE event is fired by both the sender and recipient clients.
This request can be sent if the Buddy List System is already initialized (see the InitBuddyListRequest class description).