Three additions, all driven from the simulator debug panel.
DEVICE_LOG lets a controller send text lines; they reach the simulator log
and a per connection view in the panel which keeps the last 64 of them.
Diagnostic routines: a controller lists the procedures it offers, the
operator picks one from a drop down and starts it, and the controller
reports progress and the result. While a routine runs the controller can
ask the simulator to show a message box with its own text and buttons and
gets back which one was pressed, which is what a valve or gauge
calibration needs. The message box appears whether the debug panel is
open or not.
Links can now be disconnected and reconnected by hand: disconnecting
closes the serial port so the controller can be reprogrammed, and the
session is rebuilt from scratch on reconnect. Ports which appear while
the simulation runs can be picked from a refreshed list, given a baud
rate and added as a new controller, so the manager now starts even with
no uart2 entries in eu07.ini.
The snapshot sent right after SUBSCRIBE was taken from the previous
frame, which on the first frame of a session meant every value came back
as UNAVAILABLE. The link now publishes the state of the current frame
before the received frames are processed.
Adds the logical protocol layer on top of the frame codec: session
handshake with negotiated frame size, session scoped symbol handles,
state subscriptions with periodic, on change and deadband filtering,
command events with duplicate protection and continuous controls with
stale update rejection, plus per connection rate limits and diagnostics.
A single worker thread owns all of the blocking transport work and
exchanges finished frames with the simulation thread through short locked
queues, so a stalled, flooding or unplugged controller cannot hold up the
simulation.
