opcilloscope

A lightweight, cross-platform OPC UA client for the terminal.

Browse, monitor, and subscribe to industrial automation data right from your terminal. Keyboard-driven with mouse support. No bloated GUI, no complex setup, no license fees.

Why opcilloscope?

Traditional OPC Clients	opcilloscope
Heavy desktop apps	Single self-contained executable
Minutes to install	curl | bash and you're running
Resource-hungry GUIs	Terminal-native interface
Windows-only	Windows, Linux, macOS (x64 & ARM64)
Click-heavy workflows	Keyboard-driven, mouse support

Use cases: commissioning (verify PLC tags), troubleshooting (live values during fault diagnosis), integration testing (validate OPC UA server configs), recording (export to CSV for reports).

Features

• Browse — Lazily explore the OPC UA address space. Expand only what you need.
• Monitor — Subscribe to variables with Enter. Receive OPC UA monitored-item notifications instead of polling values.
• Inspect — Full node attributes: Description, DataType, AccessLevel, ValueRank.
• Scope — Real-time multi-signal oscilloscope (up to 5 signals, 30 s sliding window).
• Record — Export selected monitored variables to CSV. Notifications are queued with full-precision, locale-independent values (ISO 8601 UTC timestamps, . decimal separator, arrays as semicolon-joined elements). A bounded queue protects the UI if storage falls behind, and any dropped records are reported when recording stops.
• Configure — Save/load connection and subscription configs (.cfg JSON files).
• Themes — Dark (default), light, and terminal (inherits your terminal's ANSI colour scheme).

Scope view — a soothing sine wave

How signal sampling works

opcilloscope does not repeatedly read each value. It creates OPC UA subscriptions and monitored items, then processes the data-change notifications delivered by the server. This is distinct from the OPC UA PubSub transport model.

OPC UA Server
  │  samples monitored items (250 ms requested by default)
  │  delivers subscription notifications (250 ms publishing interval by default)
  ▼
opcilloscope receives data-change notifications
  ├─→ Scope View     — retains up to 2,000 numeric samples per signal while open
  └─→ CSV Recording  — queues selected-variable notifications for background writes

Data capture and screen rendering are decoupled:

What	Rate	Details
Server sampling	250 ms requested	Configurable through a saved configuration; the server may revise the interval
Subscription publishing	250 ms by default	Adjustable from 100 ms to 10 s in the connect dialog
Scope redraw	10 FPS (100 ms)	Renders whatever samples arrived since last frame
CSV recording	Every accepted notification for selected variables	Uses a 10,000-record bounded queue and flushes every 10 records

The scope view starts with a sliding 30-second window (zoomable from 5 s to 300 s). It draws with Unicode braille subcells, so display resolution depends on the terminal's dimensions.

Keyboard Shortcuts

Key	Action
Tab	Cycle between panes
Enter	Subscribe to selected node
F5	Refresh address space tree
Delete	Unsubscribe from selected variable
Space	Toggle selection / pause scope
S	Open scope with selected variables
W	Write value to node
R	Toggle CSV recording (selected monitored variables)
+ / -	Zoom in / out (scope)
Ctrl+O / Ctrl+S	Open / save configuration
Ctrl+R	Toggle CSV recording
?	Help

Install

Linux / macOS:

curl -fsSL https://raw.githubusercontent.com/SquareWaveSystems/opcilloscope/main/install.sh | bash

Windows (PowerShell):

irm https://raw.githubusercontent.com/SquareWaveSystems/opcilloscope/main/install.ps1 | iex

Or grab a binary from GitHub Releases.

Release archives include the self-contained executable, the project license, and notices for bundled third-party components. The installers preserve those notices in an app-owned license directory.

The installers require the matching release checksum and refuse an unverified download. On Windows, the default install directory is added to your user PATH; a custom OPCILLOSCOPE_INSTALL_DIR is treated as shared and leaves PATH unchanged.

macOS note: the binaries are unsigned, so archives downloaded with a browser are quarantined by Gatekeeper. Either use the curl installer above, or clear the quarantine attribute after extracting: xattr -d com.apple.quarantine <binary>.

Then run:

opcilloscope

An automatic/omitted or partial security profile requires a SignAndEncrypt endpoint and selects the strongest matching candidate offered by the server. Explicit securityMode: "Sign" opts into signed-but-unencrypted traffic. Explicit anonymous securityMode: "None" opts into unsecured plaintext; username authentication never permits None.

Server certificates that fail validation are rejected by default. For a development server, opcilloscope --insecure disables server certificate validation for that run; it does not enable plaintext transport. Do not use this option in production. The connection log reports the trusted-certificate store path when validation fails.

Uninstall

Linux / macOS:

curl -fsSL https://raw.githubusercontent.com/SquareWaveSystems/opcilloscope/main/uninstall.sh | bash

Or manually on Linux:

rm ~/.local/bin/opcilloscope
rm -rf "${XDG_DATA_HOME:-$HOME/.local/share}/opcilloscope/licenses"
rm -rf "${XDG_CONFIG_HOME:-$HOME/.config}/opcilloscope"  # optional: configs and recent files
rm -rf "${XDG_DATA_HOME:-$HOME/.local/share}/opcilloscope/pki"  # optional: certificates

Or manually on macOS:

rm ~/.local/bin/opcilloscope
rm -rf "$HOME/Library/Application Support/opcilloscope/licenses"
rm -rf "$HOME/Library/Application Support/opcilloscope/configs"  # optional
rm -f "$HOME/Library/Application Support/opcilloscope/recent-files.json"  # optional
rm -rf "$HOME/Library/Application Support/opcilloscope/pki"  # optional: certificates

Windows (PowerShell):

irm https://raw.githubusercontent.com/SquareWaveSystems/opcilloscope/main/uninstall.ps1 | iex

Or manually:

$installDir = "$env:LOCALAPPDATA\Programs\opcilloscope"
Remove-Item "$installDir\opcilloscope.exe" -Force
Remove-Item "$installDir\opcilloscope-licenses" -Recurse -Force
$userPath = [Environment]::GetEnvironmentVariable("Path", "User")
$pathEntries = @($userPath -split ";" | Where-Object { $_.Trim().TrimEnd('\') -ine $installDir.TrimEnd('\') })
[Environment]::SetEnvironmentVariable("Path", ($pathEntries -join ";"), "User")
Remove-Item "$env:APPDATA\opcilloscope" -Recurse -Force             # optional: configs and recent files
Remove-Item "$env:LOCALAPPDATA\opcilloscope\pki" -Recurse -Force    # optional: certificates

If you set OPCILLOSCOPE_INSTALL_DIR, replace only the executable path above on Linux/macOS; license notices remain in the platform data directory shown above. On Windows, replace both $installDir executable/license paths with the custom directory and skip the PATH-removal lines; the installer never adds a custom directory to PATH. Configuration and certificate locations do not move. The uninstall scripts remove only files owned by opcilloscope rather than recursively deleting a shared custom install directory.

Quickstart (Developer)

Requires .NET 10 SDK.

git clone https://github.com/SquareWaveSystems/opcilloscope.git
cd opcilloscope
dotnet build Opcilloscope.sln
dotnet run --project Opcilloscope.csproj

Run the cross-platform unit, integration, and component suite:

dotnet test Opcilloscope.sln

On Linux, also exercise a freshly published binary through the real PTY E2E harness:

dotnet test Tests/Opcilloscope.E2ETests/Opcilloscope.E2ETests.csproj

See docs/TESTING.md for test layers and exact-artifact usage.

OPC UA Test Servers

Built-in test server (Counter, SineWave, RandomValue, writable nodes):

dotnet run --project Tests/Opcilloscope.TestServer
# Starts at opc.tcp://localhost:4840/UA/OpcilloscopeTest

Public servers (no setup required):

Server	Endpoint URL
OPC UA Server	opc.tcp://opcuaserver.com:48010
Eclipse Milo	opc.tcp://milo.digitalpetri.com:62541/milo

Docker (Microsoft OPC PLC):

docker run -p 50000:50000 mcr.microsoft.com/iotedge/opc-plc:latest \
  --autoaccept --unsecuretransport
# Connect to opc.tcp://localhost:50000

Contributing

Contributions welcome! Please submit an issue or a pull request, and see CONTRIBUTING.md for development and review guidance.

License

The opcilloscope source code is MIT-licensed — see LICENSE.

Official binary releases are self-contained builds that bundle the OPC Foundation UA .NET Standard stack and other third-party components. The bundled stack version (1.5.378.156) is distributed by the OPC Foundation under its MIT license; earlier versions of that stack were dual-licensed GPL-2.0/RCL. See THIRD-PARTY-NOTICES.md for the full list of bundled components and their licenses.

Built by Square Wave Systems
Inspired by lazygit