lmxopcua/docs/Driver.TwinCAT.Cli.md

otopcua-twincat-cli — Beckhoff TwinCAT test client

Ad-hoc probe / read / write / subscribe tool for Beckhoff TwinCAT 2 / TwinCAT 3 runtimes via ADS. Uses the same TwinCATDriver the OtOpcUa server does (Beckhoff.TwinCAT.Ads package). Native ADS notifications by default; --poll-only falls back to the shared PollGroupEngine.

Fifth (final) of the driver test-client CLIs.

Build + run

dotnet run --project src/ZB.MOM.WW.OtOpcUa.Driver.TwinCAT.Cli -- --help

Prerequisite: AMS router

The Beckhoff.TwinCAT.Ads library needs a reachable AMS router to open ADS sessions. Pick one:

1. Local TwinCAT XAR — install the free TwinCAT 3 XAR Engineering install on the machine running the CLI; it ships the router.
2. Beckhoff.TwinCAT.Ads.TcpRouter — standalone NuGet router. Run in a sidecar process when no XAR is installed.
3. Remote AMS route — any Windows box with TwinCAT installed, with an AMS route authorised to the CLI host.

The CLI compiles + runs without a router, but every wire call fails with a transport error until one is reachable.

Common flags

Flag	Default	Purpose
-n / --ams-net-id	required	AMS Net ID (e.g. 192.168.1.40.1.1)
-p / --ams-port	851	AMS port (TwinCAT 3 PLC = 851, TwinCAT 2 = 801)
--timeout-ms	5000	Per-operation timeout
--poll-only	off	Disable native ADS notifications, use PollGroupEngine instead
--verbose	off	Serilog debug output

Data types

TwinCAT exposes the IEC 61131-3 atomic set: Bool, SInt, USInt, Int, UInt, DInt, UDInt, LInt, ULInt, Real, LReal, String, WString, Time, Date, DateTime, TimeOfDay. The four IEC time/date variants marshal as UDINT on the wire — CLI takes a numeric raw value and lets the caller interpret semantics.

Commands

probe

# Local TwinCAT 3, probe a canonical global
otopcua-twincat-cli probe -n 127.0.0.1.1.1 -s "TwinCAT_SystemInfoVarList._AppInfo.OnlineChangeCnt"

# Remote, probe a project variable
otopcua-twincat-cli probe -n 192.168.1.40.1.1 -s MAIN.bRunning --type Bool

Health probe

The OtOpcUa server's TwinCAT driver runs an internal probe loop (PR 3.2, issue #314) that — alongside the cheap ReadStateAsync reachability check — samples four well-known system symbols once per probe interval and surfaces the result through the cross-driver driver-diagnostics RPC (added for Modbus, task #154). The same symbols can be probed directly via the CLI for ad-hoc troubleshooting:

# Cycle time (UDINT, 100 ns ticks → ÷10000 for ms)
otopcua-twincat-cli probe -n 192.168.1.40.1.1 -s "TwinCAT_SystemInfoVarList._TaskInfo[1].CycleTime" --type UDInt

# Last task execution wall-clock (UDINT, 100 ns ticks → ÷10000 for ms)
otopcua-twincat-cli probe -n 192.168.1.40.1.1 -s "TwinCAT_SystemInfoVarList._TaskInfo[1].LastExecTime" --type UDInt

# Online-change count — increments on every accepted online change
otopcua-twincat-cli probe -n 192.168.1.40.1.1 -s "TwinCAT_SystemInfoVarList._AppInfo.OnlineChangeCnt" --type UDInt

# Loaded PLC project name (STRING(80))
otopcua-twincat-cli probe -n 192.168.1.40.1.1 -s "TwinCAT_SystemInfoVarList._AppInfo.AppName" --type String

Within the running OtOpcUa server these four signals land on DeviceState.LastDiagnostics as a TwinCATDeviceDiagnostics record + are folded into DriverHealth.Diagnostics keyed TwinCAT.CycleTimeMs, TwinCAT.LastExecTimeMs, TwinCAT.JitterMs (computed LastExecTimeMs - CycleTimeMs), TwinCAT.OnlineChangeCnt, and TwinCAT.OnlineChangeIncrements. See docs/drivers/TwinCAT-Test-Fixture.md §Diagnostics for the full mapping.

read

# Bool symbol
otopcua-twincat-cli read -n 192.168.1.40.1.1 -s MAIN.bStart -t Bool

# Counter
otopcua-twincat-cli read -n 192.168.1.40.1.1 -s GVL.Counter -t DInt

# Nested UDT member
otopcua-twincat-cli read -n 192.168.1.40.1.1 -s Motor1.Status.Running -t Bool

# Array element
otopcua-twincat-cli read -n 192.168.1.40.1.1 -s "Recipe[3]" -t Real

# WString
otopcua-twincat-cli read -n 192.168.1.40.1.1 -s GVL.sMessage -t WString

ADS variable handles for read / write symbols are cached transparently inside the CLI's underlying AdsTwinCATClient. The first read of a symbol resolves a handle; repeats reuse the cached handle for smaller AMS payloads and skipped name resolution. The cache wipes on reconnect, on DeviceSymbolVersionInvalid (with a one-shot retry), and on CLI exit. See docs/drivers/TwinCAT-Test-Fixture.md §Handle caching for the full story including the staleness caveat after an online change.

write

otopcua-twincat-cli write -n 192.168.1.40.1.1 -s MAIN.bStart -t Bool -v true
otopcua-twincat-cli write -n 192.168.1.40.1.1 -s GVL.Counter -t DInt -v 42
otopcua-twincat-cli write -n 192.168.1.40.1.1 -s GVL.sMessage -t WString -v "running"

Structure writes refused — drop to driver config JSON for those.

subscribe

# Native ADS notifications (default) — PLC pushes on its own cycle
otopcua-twincat-cli subscribe -n 192.168.1.40.1.1 -s GVL.Counter -t DInt -i 500

# Fall back to polling for runtimes where native notifications are constrained
otopcua-twincat-cli subscribe -n 192.168.1.40.1.1 -s GVL.Counter -t DInt -i 500 --poll-only

# Coalesce bursty changes — runtime buffers up to 500 ms before dispatch
otopcua-twincat-cli subscribe -n 192.168.1.40.1.1 -s GVL.Counter -t DInt -i 50 --max-delay-ms 500

Flag	Default	Purpose
-s / --symbol	required	Symbol path — same format as read
-t / --type	DInt	IEC type (see Data types section)
-i / --interval-ms	1000	Cycle time — minimum interval between change checks the PLC runtime applies
--max-delay-ms	0	Max coalescing window — upper bound on how long the runtime buffers change events before dispatch. 0 = fire ASAP, no coalescing
--poll-only	off	Disable native notifications, use PollGroupEngine instead

-i / --interval-ms and --max-delay-ms are different things and both flow into the Beckhoff NotificationSettings ctor:

• --interval-ms is the cycle: the runtime checks for value changes at most this often. Smaller = lower latency, higher CPU.
• --max-delay-ms is the coalescing ceiling: once a change is detected, the runtime can hold it for up to this long before dispatching, which lets it batch a burst of changes into a single callback. Default 0 means every detected change fires immediately — same as the pre-PR-3.1 behaviour.

For high-frequency signals (a counter incrementing every 10 ms PLC cycle), pair a small -i (so latency stays bounded) with a non-zero --max-delay-ms (so the OPC UA queue downstream doesn't flood). For slow signals just leave --max-delay-ms at 0.

The subscribe banner announces which mechanism is in play — "ADS notification" or "polling" — and includes the max-delay value when set, so it's obvious in screen-recorded bug reports.

--poll-only polls go through the same cached-handle path as read, so repeated polls of the same symbol carry only a 4-byte handle on the wire rather than the full symbolic path.