Native ADS notifications (the default subscribe mode) were stored as opaque handles
with no record of the symbol/type/interval/handler needed to replay. On a client swap
(EnsureConnectedAsync building a fresh client after a drop) the notifications were
silently orphaned — no Bad status, no error, pushes just stopped until redeploy.
Compounding: the IsConnected fast-path keys on AMS-port state, not wire liveness, and
a probe failure only transitioned state without recycling the dead client.
Fix:
- Store REPLAYABLE INTENT: NativeRegistration (symbol/type/bit/interval/onChange +
swappable live handle) hung off DeviceState.NativeRegistrations, populated by
SubscribeAsync via RegisterNotificationAsync (under ConnectGate).
- Split EnsureConnectedAsync into a gate wrapper + EnsureConnectedUnderGateAsync core;
when the core installs a NEW client it replays every stored intent onto it and swaps
the live handle (disposing the dead one). Register + replay both run under ConnectGate
so they can't race.
- Probe loop: on a wire-probe failure (false or throw) RecycleClientAsync disposes+nulls
the client so the next tick rebuilds + replays — closes the fast-path-keys-on-port-state
compounding bug.
No TwinCAT docker fixture exists (integration needs a real TC3 XAR), so the fake-client
unit tests are the authoritative coverage:
- 4 new guards in TwinCATReconnectReplayTests (replay-onto-fresh-client + push reaches
OnDataChange + old handle disposed; replay-all-tags; unsubscribe-after-reconnect stops
replaying; probe-failure recycles+rebuilds).
- Full TwinCAT unit suite 174/174 green; full solution builds 0 errors.
Joseph Doherty