Mailboxes
Threads exchange information by sending messages to and receiving messages from mailboxes. Any thread can send information to a mailbox, and any thread can receive information from a mailbox.
Two types of mailboxes are available. The type of mailbox is specified when the mailbox is created.
Data mailboxes are used to send or receive messages of up to 128 bytes of data.
Object mailboxes are used to send or receive handles for RT objects. Object mailboxes can be used with memory handles to make large amounts of data available.