DNPScop Slave is a free DNP3 (IEEE 1815) outstation simulator with a modern, dockable Dear ImGui interface — a companion to ModbusScop Master and Slave, sharing their look and feel. It emulates many DNP3 outstations at once over TCP, UDP, and serial channels, so engineers can test, commission, and troubleshoot DNP3 masters and SCADA systems without real field hardware.
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 Slave is organized as a tree: Channels → Outstations → Point groups.
- A Channel is one server endpoint: a TCP listener (serving several masters at once, up to a configurable limit), a UDP datagram server, or a Serial line carrying DNP3 link frames. Each channel runs on its own I/O thread; start and stop them independently.
- An Outstation is one simulated device with its own link address behind a channel. A channel can host many outstations; each frame is routed to the outstation whose link address matches (with an optional catch-all).
- Each outstation carries a full point database — Binary/Double-bit Inputs, Binary/Analog Outputs, Analog Inputs, Counters and Frozen Counters — editable directly in the UI, each point with its own static and event variations.
- Complete hand-rolled DNP3 stack over Asio (no third-party DNP3 library): link layer with per-block CRCs, transport segmentation/reassembly, and the application layer with the full object/qualifier codec.
- TCP, UDP, and Serial channels — serve masters over DNP3-over-TCP, DNP3-over-UDP, or a serial line, chosen per channel. DNP3's self-framing link layer means the same engine deframes a stream, a datagram, or a serial line identically.
- Multi-outstation, multi-master — many channels, each with many outstations on distinct link addresses; TCP channels serve multiple masters concurrently.
- Full point model — Binary Inputs, Double-bit Binary Inputs, Binary Outputs, Analog Inputs, Analog Outputs, Counters and Frozen Counters, with per-point static and event variations.
- Reads, classes, and events — static reads (Class 0) and event reads (Classes 1/2/3) served from per-class event buffers with configurable overflow policy; integrity polls and enable/disable unsolicited.
- Unsolicited responses — outstations push events to connected masters as they occur, with confirmation handling.
- Controls + glue logic — CROB (Trip/Close, pulse/latch) and analog-output operate/select; map an operated control to a point action so commanding an output drives the matching input, and pass analog-output setpoints through to analog inputs.
- Per-point simulation — Sine, Ramp, Random, Counter, Toggle, and double-bit state walk, constrained by each point's type and paced per point.
- Time & Date — System or Manual time source, Local / UTC display with a DST-aware offset, and a per-outstation GMT offset applied on the wire.
- Communication Monitor — a timestamped, filterable log of every frame with a layered link/transport/application decode, per master and per outstation.
- Status Messages & Dashboard — channel start/stop and master connect/disconnect events, plus live per-channel traffic counters and uptime.
- Workspaces — save and reload your entire setup: channels (including transport), outstations, points, values, variations, glue logic, and simulations.
- Themes — dark / light / classic with a customizable accent color; layout and preferences are remembered between runs.
- Go to the Releases page and download the latest
DNPScopSlavearchive for Windows. - Unzip it anywhere and run
DNPScopSlave.exe— no installation required.
Requirements: Windows 10/11 (64-bit).
Rendering: DNPScop Slave uses the GPU by default; you can switch to CPU (software) rendering under View → Rendering (handy over Remote Desktop or in VMs).
- New Channel — choose TCP or UDP, set the bind IP and port (DNP3 commonly uses 20000), and — for TCP — the maximum number of masters. Or use New Serial Channel for a serial line. Each new channel starts with one outstation (link 1).
- Add outstation — add more outstations, each with its own link address.
- Edit the outstation's points — set values, variations, controls/glue, and per-point simulation.
- Press Start on the channel and point your DNP3 master at the endpoint. Watch the frames decode in the Communication Monitor and the counters in the Dashboard.
Use File → Save Workspace to keep the whole configuration and reload it later.
DNPScop Slave 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, point database, event buffers, outstation engine) is original code, not a third-party library.
DNPScop Slave 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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and/or other materials provided with the distribution.
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