Replace the bare TCP-connect probe in ModbusDriverProbe with a two-phase
check: TCP connect via ModbusTcpTransport (keeps the same SocketException /
timeout / generic error paths and messages), then a one-shot FC03 Read
Holding Registers (qty 1 @ addr 0). A normal response → Ok=true "Modbus
FC03 OK"; a Modbus exception PDU → Ok=true "Modbus FC03 OK (device
returned exception PDU)"; any other failure after TCP succeeds → Ok=false
"Reachable at host:port but Modbus FC03 handshake failed: …".
Add ModbusDriverProbeTests (6 tests) covering invalid JSON, missing
host/port, closed port, TCP-accept-then-close, canned MBAP happy path,
and Modbus exception PDU path. All 277 Modbus tests green.
ModbusDriverProbe.DriverType was "Modbus" but the AdminUI's
ModbusDriverPage persists DriverInstance.DriverType = "ModbusTcp".
GalaxyDriverProbe used the runtime DriverTypeName constant
("GalaxyMxGateway") but the AdminUI saves "Galaxy". The probe DI
lookup is case-insensitive but not name-insensitive, so Test
Connect would fail to find a probe for these two drivers.
Cheap-and-fast probe: open TCP socket to the configured endpoint,
close immediately. Surfaces SocketError on failure, latency on
success, "timed out" on caller cancel. Sufficient for the AdminUI
Test Connect "can we reach the host?" question. Richer protocol-
level probes (OPC UA session open, FOCAS handshake, gRPC ping)
are a documented follow-up. Each probe registered as
AddSingleton<IDriverProbe, X> in DriverFactoryBootstrap so they
flow through DI into AdminOperationsActor.
Historian.Wonderware returns a clean "TCP probe not applicable"
result because it communicates over a Windows named pipe, not TCP.
Also adds OpcUaClient + Historian.Wonderware.Client project
references to Host.csproj (both were missing from the driver
ItemGroup).
Joseph Doherty