Web Print Service

A cross-platform .NET 8.0 print service that connects to a web application via SignalR and provides remote printing. Automatically detects the operating system and uses Windows Print (PowerShell/WMI) on Windows or CUPS (lpstat, lp) on Linux/macOS.

Architecture

Windows

Web App (BasicWeigh, etc.)
    |
    +-- SignalR Hub (/scaleHub)
            |
            +-- Web Print Service (this)
                    |
                    +-- SumatraPDF (silent PDF printing)
                            |
                            +-- Physical Printer (USB, Network, Shared)

Windows PDF Printing Requirements

The service needs a silent PDF printing tool to send tickets to printers. It auto-detects in this order:

1. SumatraPDF (recommended) — auto-installed via winget if not found
2. PDFtoPrinter.exe — if placed in the service directory
3. Fallback — uses Start-Process -Verb PrintTo (may open a dialog, not recommended for unattended use)

To manually install SumatraPDF:

winget install SumatraPDF.SumatraPDF

Or download from https://www.sumatrapdfreader.org/free-pdf-reader

Linux / macOS / Raspberry Pi

Web App (BasicWeigh, etc.)
    |
    +-- SignalR Hub (/scaleHub)
            |
            +-- Web Print Service (this)
                    |
                    +-- CUPS (lpstat, lp, lpoptions)
                            |
                            +-- Physical Printer (USB, Network, IPP)

Features

• Cross-Platform — automatically uses Windows Print or CUPS based on the OS
• Windows Integration — uses PowerShell Get-Printer, Start-Process, Out-Printer to manage and print to local and network printers
• CUPS Integration — uses lpstat, lp, lpoptions to manage and print to local printers on Linux/macOS
• SignalR Connection — connects to any web app's SignalR hub (outbound only, works behind firewalls)
• Printer Discovery — announces available CUPS or Windows printers to the web app on connect/reconnect
• PDF Printing — downloads ticket PDFs from the web app and prints locally
• Test Print — send a test page to any connected printer from the web UI
• Swagger API — local REST API for configuration, testing, and diagnostics
• SQLite Settings — persistent configuration stored locally (no appsettings.json edits needed)
• Forever Retry — exponential backoff, never gives up reconnecting

Quick Start

# Windows
cd WebPrintService
dotnet run

# Linux / Raspberry Pi
sudo apt-get install cups
dotnet run

Endpoints (Swagger at http://:/swagger)

Health & Status

GET /api/status/health

Returns service health, print system type, and printer count.

Response:

{
  "status": "ok",
  "printSystem": "Windows",
  "printSystemAvailable": true,
  "printerCount": 3,
  "printers": [
    { "printerId": "HP LaserJet", "displayName": "HP LaserJet", "status": "idle", "enabled": true, "isDefault": true }
  ]
}

GET /api/readme

Returns API documentation as JSON including all endpoints, parameters, response formats, and SignalR methods.

---

Printers

GET /api/printers

List all printers with their status.

Response:

[
  {
    "printerId": "HP_LaserJet_Pro",
    "displayName": "HP LaserJet Pro",
    "status": "idle",
    "isDefault": true,
    "enabled": true
  }
]

GET /api/printers/{printerId}/status

Get detailed status of a specific printer.

Example: GET /api/printers/HP_LaserJet_Pro/status

Response:

{
  "printerId": "HP_LaserJet_Pro",
  "status": "printer HP_LaserJet_Pro is idle. enabled since Mon 24 Mar 2026 08:00:00 AM CDT"
}

POST /api/printers/{printerId}/test

Send a test page to a printer. No request body needed.

Example: POST /api/printers/HP_LaserJet_Pro/test

Response:

{
  "success": true,
  "message": "Sent to HP_LaserJet_Pro"
}

---

Settings

GET /api/settings

Get current service settings.

Response:

{
  "id": 1,
  "serviceId": "default",
  "serverUrl": "http://localhost:5110",
  "signalRHub": "/scaleHub"
}

PUT /api/settings

Update service settings. Triggers a reconnect to the web app.

Request:

{
  "serviceId": "office-printer",
  "serverUrl": "http://192.168.1.100:5110"
}

Response:

{
  "success": true,
  "message": "Settings saved. Service restarting..."
}

---

SignalR Methods

Direction	Method	Description
Service -> Hub	JoinPrintGroup(serviceId)	Join the PrintClients group
Service -> Hub	PrintServiceReady(announcement)	Announce printers on connect
Service -> Hub	PrinterListResponse(data)	Respond to printer list request
Service -> Hub	PrintResult(result)	Report print job result
Service -> Hub	TestPrintResult(result)	Report test print result
Hub -> Service	PrintTicket(data)	Print a ticket PDF
Hub -> Service	GetPrinterList	Request printer list
Hub -> Service	TestPrint(printerId)	Send test page to printer
Hub -> Service	ReloadConfig	Restart the service

Platform Details

Windows

Uses PowerShell commands:

• Get-Printer — enumerate all local and network printers
• Start-Process -Verb PrintTo — print PDFs (or SumatraPDF if installed)
• Out-Printer — print text files
• rundll32 shimgvw.dll — print images
• Optional: SumatraPDF for better PDF printing

Linux / macOS (CUPS)

Uses CUPS command-line tools:

• lpstat -p -d — enumerate printers and default
• lp -d <printer> — print files
• lpoptions -p <printer> — get printer options/description
• CUPS web interface at https://localhost:631

Deployment

Install on Raspberry Pi / Linux

SSH into the Pi and run:

git clone https://github.com/GTMichelli-Dev/web-print-service.git /tmp/wps
bash /tmp/wps/deploy/install.sh https://basicscale.scaledata.net
rm -rf /tmp/wps

With options:

git clone https://github.com/GTMichelli-Dev/web-print-service.git /tmp/wps
bash /tmp/wps/deploy/install.sh https://basicscale.scaledata.net \
    --service-id office --port 5230
rm -rf /tmp/wps

For private repos, git will prompt for credentials. You can also use a deploy key or GitHub token.

Options:

Option	Default	Description
--service-id <id>	default	Unique ID for this service instance
--port <port>	5230	API/Swagger port
--branch <branch>	master	Git branch to install
--install-dir <path>	/opt/web-print-service	Install location

What the script does automatically:

1. Detects Pi architecture (arm64, armv7l, x64)
2. Installs CUPS (printer system)
3. Installs .NET 8 SDK and runtime permanently (skips download on future updates)
4. Downloads latest source from GitHub
5. Builds for the Pi's architecture
6. Installs to /opt/web-print-service
7. Preserves existing database on updates
8. Registers and starts as a systemd service

Prerequisites: Just internet access and git (pre-installed on Raspberry Pi OS). No .NET, no CUPS — the script installs everything. The .NET SDK is installed permanently so future updates skip the download.

To update: Run the same command again. The script stops the service, updates files, preserves your database, and restarts.

After install:

• Swagger: http://<pi-ip>:5230/swagger
• CUPS Admin: http://<pi-ip>:631
• Logs: sudo journalctl -u web-print-service -f
• Restart: sudo systemctl restart web-print-service

Install on Windows

Option A — Automated (as a Windows Service):

Run PowerShell as Administrator:

.\deploy\deploy-to-windows.ps1 -WebServerUrl "https://basicscale.scaledata.net"

# With options
.\deploy\deploy-to-windows.ps1 -WebServerUrl "https://basicscale.scaledata.net" `
    -ServiceId "office" -Port 5230

Parameter	Default	Description
-WebServerUrl	(required)	BasicWeigh web server URL
-ServiceId	default	Unique ID for this instance
-Port	5230	API/Swagger port
-InstallDir	C:\Services\WebPrintService	Install location
-ServiceName	WebPrintService	Windows service name

What the script does: Installs .NET if needed, builds, installs to C:\Services\WebPrintService, preserves existing database, registers as a Windows Service with auto-restart on failure.

After install:

• Swagger: http://localhost:5230/swagger
• Manage: services.msc > "Web Print Service"
• Restart: Restart-Service WebPrintService

Option B — Manual (for development):

cd WebPrintService
dotnet run

Windows printers are auto-detected — no additional setup needed.

Configuration

Initial config via appsettings.json:

{
  "Print": {
    "ServerUrl": "https://your-server",
    "Port": "5230"
  }
}

After first run, use the API to update settings (persists to SQLite):

curl -X PUT http://localhost:5230/api/settings \
  -H "Content-Type: application/json" \
  -d '{"serverUrl": "https://your-server", "serviceId": "office-printer"}'