● Beta opens June 2026 · v0.9.4Modbus RTU / TCP / ASCIIClient · Server · Scan · Dashboard · Script
Coilware Modbus

A Modbus client
that respects your time.

Diagnose, debug, commission and document any Modbus device with a tool that doesn't look or feel like it was written in 2004. Client, server simulator, network scanner, live dashboard and Python scripting - one application.

Beta opens June 2026 · perpetual licence £179 · 30-day refund, no questions

Modbus Tools - Default workspace
Modbus Tools/Modbus TCP ClientSE
Polling · 500 ms
Search registers
FCAddressNameDisplay asValueUnitTrend
FC03Voltages - line to neutral40001 – 40006
FC0340001Voltage L1–NF32230.48V
FC0340003Voltage L2–NF32229.72V
FC0340005Voltage L3–NF32230.94V
FC03Power & energy40013 – 40020
FC0340013Active Power TotalF329813.75W
Byte-order decode · 2-register FLOAT32
OrderFloat32UInt32Int32
ABCD9813.751,176,065,7931,176,065,793
CDAB1.42e+141,459,701,2731,459,701,273
BADC1.02e-23424,018,263424,018,263
DCBA3.95e-3822,485,31822,485,318

Highlighted orders decode to a plausible value - click to apply.

Register · 40013
Function code
0x03 · Read Holding Registers
Word count
2
Display type
F32 · ABCD
Polled
every 500 ms
FC0340015Power FactorF320.97-
FC0340017FrequencyF3250.05Hz
FC0340019kWh ImportU32184,272Wh
FC04Line currents30001 – 30006
FC0430001Current L1F3214.72A
FC0430003Current L2F3213.91A
FC0430005Current L3F3214.07A
FC01Relay outputs00001 – 00002
FC0100001Relay K1 - TripBit0--
FC0100002Relay K2 - AlarmBit1--
FC02Interlocks10001 – 10002
FC0210001Door interlockBit1--
FC0210002Earth-fault inputBit0--
Connected·tcp://10.34.18.221:502·RTT 8 ms·41 ops/sWorkspaceDefault·v0.9.4
Features

Built around how you actually debug.

01 · LIVE REGISTERS

Holding, input, coil, discrete - all four spaces, one view.

Typed register reads with auto-scaling, engineering units, and quality indicators. Edit cells in place to write back to the device. Polled at configurable intervals. Sortable by address, name, last change, or quality.

  • FLOAT32, INT16/32/64, UINT16/32/64, BCD, ASCII, custom
  • Per-register byte order - override the global default
  • Quality flags: live, stale, exception, timeout
  • Transparent request chunking - 500 registers becomes 4 conformant reads
01
02 · FRAME INSPECTOR

Every byte on the wire, decoded.

A capture timeline of every TX/RX frame, with the function code named, the CRC checked, and the payload interpreted. Filter, search, export to annotated CSV. The first tool you reach for when something silent goes wrong.

  • Raw TX/RX trace with per-exchange timestamps
  • Function-code-aware payload decode
  • CRC / MBAP transaction-ID validation with mismatch highlighting
  • Export to CSV or JSON
02
03 · DECODER

Endianness, finally, visible.

See any register as FLOAT32, INT32, UINT32 and packed BCD under all four byte orders - ABCD, CDAB, BADC, DCBA - at once. The “1.3 × 10⁻¹³ instead of 230 V” bug, solved in eight seconds.

  • Side-by-side comparison of all four orderings
  • Hex · decimal uint16 · signed int16 · binary, simultaneously
  • Save a chosen order as a per-register preset
  • Works on captured frames from the Inspector
03
Specs

No surprises in the readme.

Platforms
Windows
10, 11 · x64
Runtime
.NET 8 · self-contained build
Roadmap
macOS + Linux under evaluation
Headless
CLI mode for CI / on-box use
Protocols
Modbus TCP
Stable
Modbus RTU
In progress
Modbus ASCII
In progress
Function codes
Read
FC01 · FC02 · FC03 · FC04
Write
FC05 · FC06 · FC15 · FC16
Mask
FC22 - Mask Write Register
Identify
FC17 · FC43 / MEI-0x0E
Licensing
Trial
30 days, full features, offline
Personal
£179 · 1 user · 2 machines
Team
£599 · 5 seats · floating
Site
POA · unlimited seats per site
Students
Free · with academic ID
Anti-features

What it won't do to you.

✕ NO

No subscription

One price. Perpetual. You own the licence. No-network mode supported indefinitely.

✕ NO

No USB dongle

We mean it. No HASP, no Aladdin, no SafeNet. Activation by licence file or offline key.

✕ NO

No admin install

Single binary. Drop on a thumb drive. Run on the locked-down plant laptop your IT team set up in 2017.

✕ NO

No telemetry

No analytics, no crash reporters phoning home, no ‘help us improve’ dialogs. Opt-in error reports only.

✕ NO

No cloud lock-in

Config files are open formats. Captures export to CSV/JSON. Leave anytime.

✕ NO

No AI features (yet)

We're not gluing an LLM to the dialog box this year. If we do, it'll be optional and local.

Beta access

Want a free perpetual licence?

First twenty beta testers get a free perpetual licence - for life - in exchange for using it on real work and telling us what's broken.