Secure Session API frames

Secure Session can only be established from a node that is operating in API mode. The server-side can be in Transparent mode, but the client must be in API mode. Once a session has been established between a client and server node, the client can be transitioned to Transparent mode; and if bit 4 of TO is set, the client will encrypt data sent in Transparent mode for the duration of session.

There are four frames that are used for controlling and observing a secure session.

• Secure Session Control - 0x2E: This frame is passed to the client that wishes to log into or out of a server. Any attempt to use the Control frame will generate a response frame.
• Secure Session Response - 0xAE: This frame returns the status of the previously sent 0x2E frame indicating whether it was successful or not.
• Modem Status - 0x8A: The server will also emit a modem status whenever an attempt succeeds, fails, or was terminated. The client will also emit modem statuses if the session times out.
• Extended Modem Status - 0x98: If bit 3 of AZ is set then modem statuses will be replaced with extended modem statuses. These frames will contain the status that caused them to be emitted as well as the address of the node that initiated the session, the session options, and the timeout value.

Frame exchanges: