echo — Group 0, Code 00

Connectivity and request/response sanity check.

Purpose

Use echo when you need to confirm that a specific RAIDA is reachable and able to complete a basic round trip. It is the lowest-risk probe in the live surface.

Typical client use

Run echo before expensive multi-RAIDA work, or when you need a quick liveness probe for diagnostics and dashboards.

Request body (18 bytes)

The body is just the encrypted challenge plus the protocol terminator. The framework verifies the challenge CRC and the terminator before cmd_echo runs, so the handler itself reads no body fields.

CH CH CH CH CH CH CH CH CH CH CH CH CH CH CH CH 3E 3E

Request packet diagram

Challenge (16 bytes, part 1 of 2) 0 7 Challenge (part 2 of 2) 8 15

Bytes 16-17 carry the fixed 3E 3E protocol terminator.

Response

No body. The status byte in the response header indicates the outcome (0xFA = STATUS_SUCCESS).