Programming Internet Email

ACAP Commands

ACAP sessions, states, and commands are very similar to IMAP4revl. This is intentional, since the protocol structure defined in IMAP is very flexible. ACAP, like IMAP and many other Internet protocols, is line oriented with lines ending in CRLF sequences.

ACAP sessions may be in one of three states at anyone time. These states are:

• Nonauthenticated State

• Authenticated State

• Logout State

Upon initial connection to an ACAP server, a client is in the Nonauthenticated State. A client enters the Authenticated State when a user logs into the server, providing the appropriate type of authentication credentials.

Once logged in, a client may search, add, or remove information in any dataset for which the authenticated user has been allowed access.

The Logout State is entered when a client logs out, a server refuses service, or a connection is otherwise interrupted. This state lasts just long enough for the client and server to close a connection.

Within each state, the client may issue the commands appropriate to that state.

Like IMAP, an ACAP client is required to be able to accept any server response at any time. This recognizes the multithreaded nature of modern MUAs, since they may very well issue multiple commands to a server simultaneously from different threads.

An ACAP client precedes each command with a pseudo-random alphanumeric string, or tag. This is done exactly as in IMAP commands. Server responses include a copy of the tag so that the client may determine to which command ...