DNPScop Master is a free DNP3 (IEEE 1815) master / controlling-station tool with a modern, dockable Dear ImGui interface — the companion to DNPScop Slave, sharing its look and feel. It talks to real outstations over TCP, UDP, and serial channels, so engineers can poll, command, and troubleshoot RTUs, IEDs, and gateways in the field or on the bench.
The complete DNP3 stack — link, transport, and application layers — is hand-rolled over Asio, with no third-party protocol library.
Free to use and redistribute under the permissive BSD 2-Clause License.
Developed by Carlos Nardi.
DNPScop Master is organized as a tree: Channels → RTUs → Points.
- A Channel is one connection: a TCP client, a UDP endpoint, or a Serial line carrying DNP3 link frames. Each channel has its own master link address and response timeout, runs on its own I/O thread, and can be started and stopped independently. TCP and serial channels can auto-reconnect when the link drops.
- An RTU is one outstation with its own link address behind a channel. A channel can host many RTUs — a multi-drop serial line or a terminal server fronting several IEDs — and every response is routed to the RTU whose link address matches. Each RTU shows a live online / offline indicator.
- Each RTU carries a message schedule (what the master sends, and when) and a point map — named Binary Inputs, Double-bit Inputs, Analog Inputs, Counters, Frozen Counters, Binary Outputs, and Analog Outputs — plus a view of the outstation's Internal Indications.
- Complete hand-rolled DNP3 stack over Asio (no third-party DNP3 library): link layer with per-block CRCs, transport segmentation/reassembly, and an application layer that decodes the standard variations of groups 1, 2, 3, 4, 10, 11, 20, 21, 22, 23, 30, 32, 40, and 42 — 16/32-bit integers, floats and doubles, with or without flags and time tags.
- TCP, UDP, and Serial channels — connect over DNP3-over-TCP, DNP3-over-UDP, or a serial line, chosen per channel; multiple RTUs per channel with per-RTU link addresses; automatic 5-second reconnect for TCP and serial.
- Per-RTU message schedule — a live, editable Messages window with four phases: Communication Start (a response-gated, ordered one-shot sequence such as Reset Link → Class 0 read → Clear Restart → Enable Unsolicited), Integrity, Cyclic, and Idle, each row with its own period and a live Next in countdown. Rows blink as they are sent.
- Presets by DNP3 level — choose the outstation's conformance level (1 / 2 / 3) and Suggest from level seeds a sensible schedule: Class 0 integrity for every level, Class 1/2/3 event polling for Level 2, unsolicited enable for Level 3. Then add, remove, or tune any message.
- Rich message library — Reset Link, Link Status, class reads (Class 0, 1, 2, 3 and combinations), group/variation reads (g1, g3, g10, g20, g21, g30, g40 with every standard variation), Enable / Disable Unsolicited per class combination, Clear Restart, Cold Restart, and Write Time (time sync).
- Controls — operate Binary Outputs with CROB (Latch On/Off, Pulse On/Off, Trip, Close, with count and on/off times) and Analog Outputs as 16-bit, 32-bit, or float, in Direct Operate, Direct Operate (no ack), or Select-Before-Operate mode; an Auto toggle option flips the command after each send. Command results (Success, Timeout, Not Supported, …) are shown per point.
- Unsolicited responses — imaged and confirmed automatically as they arrive, and tagged separately in the Events list.
- Live Data Map — the raw received image of any RTU (group, index, value, quality flags, static/event source, device time) with type, index, and value filters.
- Points windows — per-RTU named maps in Indications, Measurands, Counters, Controls, and Internal Indications tabs; sortable, multi- select editing, engineering scaling of integer measurands (Int16 / Int32 raw range → Eng Min / Eng Max with units), and CSV export / import compatible with DNPScop Slave's point files.
- Internal Indications — every IIN1 / IIN2 bit decoded and highlighted, live in the tree and in the Points window.
- Events — a per-channel event list (static, event, and unsolicited rows) with RTU and type/index/name/value filters, Ignore static mode, and CSV export.
- New-value animation — point rows flash when a value changes and the Channels tree blinks on traffic; color and fade speed are configurable under Setup → Animation.
- Communication Monitor — a timestamped, filterable log of every frame per channel and RTU, with a layered link/transport/application decode of the selected frame, optional log-to-file with size-based rotation.
- Status Messages & Dashboard — connection events, timeouts, and command results, plus live per-channel Tx / Rx / Timeout counters.
- Workspaces — save and reload your entire setup (
.dnmw): channels (including transport and reconnect), RTUs, message schedules, and point maps with scaling. Recent workspaces are one click away. - Themes — dark / light / classic with a customizable accent color, DPI scaling, and always-on-top; layout and preferences are remembered between runs.
- Go to the Releases page and download the latest
DNPScopMasterarchive for Windows. - Unzip it anywhere and run
DNPScopMaster.exe— no installation required.
Requirements: Windows 10/11 (64-bit).
Rendering: DNPScop Master uses the GPU by default; you can switch to CPU (software) rendering under View → Rendering (handy over Remote Desktop or in VMs).
- + Channel — choose TCP, UDP, or Serial, set the host and port (DNP3 commonly uses 20000) or the COM port parameters, the master link address, the response timeout, the first RTU's link address, and its DNP3 level. Each new channel starts with one RTU whose schedule is seeded from that level.
- Add RTU... — add more outstations to the channel, each with its own link address.
- Open the RTU's Messages window to review the schedule, or its Points window to name the points you care about and enable scaling.
- Press Start on the channel. The Communication Start sequence runs, then the integrity and cyclic polls take over; watch the frames decode in the Communication Monitor, values arrive in the Live Data Map, and counters move in the Dashboard. Use Operate.. on a control point to send commands.
Use File → Save Workspace (Ctrl+S) to keep the whole configuration and reload it later with Open Workspace (Ctrl+O).
DNPScop Master is built with these open-source components, each under its own license:
| Library | Used for | License |
|---|---|---|
| Dear ImGui (docking) | user interface | MIT |
| GLFW 3 | window / OpenGL context | Zlib/libpng |
| OpenGL 3 | rendering | — |
| Asio (standalone) | DNP3 TCP / UDP / serial transport | Boost Software License 1.0 |
| stb_image | logo / splash decoding | MIT / public domain |
The DNP3 protocol stack itself (link / transport / application layers, request builders, response parser, master engine) is original code, not a third-party library.
DNPScop Master is released under the BSD 2-Clause License. It is provided "as is", without warranty of any kind; the author is not responsible for any damage or loss caused by its use.
BSD 2-Clause License
Copyright (c) 2026, Carlos Nardi
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