Local Printers Windows App

A lightweight Windows middleware that receives pre-rendered print-ready HTML from Frappe/ERPNext via Socket.IO, converts it to PDF, and silently prints to the designated local printers.

How It Works

ERPNext (Sales Invoice Submit)
  └─► Frappe app renders HTML using chosen Print Format (server-side)
        └─► Socket.IO event → sends { html, printer, invoice_name, … }
              └─► This Windows app receives the event
                    └─► wkhtmltopdf converts HTML → PDF
                          └─► SumatraPDF silently prints to local printer

All HTML rendering and template logic lives in the Frappe app (local_printers). The Windows app is a thin print client — it only converts HTML to PDF and prints.

Prerequisites

• Python 3.10+
• Windows OS (uses win32print)
• SumatraPDF (silent PDF printing)
• wkhtmltopdf (HTML → PDF conversion)
• Frappe/ERPNext with the local_printers app installed

Installation

git clone https://github.com/Ahmed-Mansy-Mansico/local_printers_winapp.git
cd local_printers_winapp
pip install -r requirements.txt

Configuration

Copy config copy.json to config.json and fill in your values:

{
  "FRAPPE_SOCKET_URL": "https://your-site.com",
  "LOGIN_URL": "https://your-site.com/api/method/login",
  "AUTH_DATA": {
    "usr": "your-username",
    "pwd": "your-password"
  },
  "API_KEY": "your-api-key",
  "API_SECRET": "your-api-secret",
  "WKHTMLTOPDF": "C:\\Program Files\\wkhtmltopdf\\bin\\wkhtmltopdf.exe",
  "SUMATRA_PDF_PATH": "C:\\Program Files\\SumatraPDF\\SumatraPDF.exe"
}

Key	Description
FRAPPE_SOCKET_URL	Your ERPNext site URL
LOGIN_URL	Login endpoint (usually {site}/api/method/login)
AUTH_DATA	Credentials for Socket.IO session
API_KEY / API_SECRET	API token for printer registration
WKHTMLTOPDF	Path to wkhtmltopdf.exe
SUMATRA_PDF_PATH	Path to SumatraPDF.exe

Usage

python socket_app.py

The app will:

1. Load config and log in to your Frappe site
2. Connect via Socket.IO and register local printers
3. Listen for sales_invoice_submitted events
4. Convert received HTML to PDF and print silently

Print Format Setup (Server Side)

In ERPNext, go to Printer Item Group and configure:

• POS Profile — which POS triggers this printer
• Printer — the local printer name (auto-discovered)
• Print Format — choose which Print Format to render (Link field)
• No Letterhead — skip letterhead if needed
• Item Groups — route specific item categories to this printer

The Frappe app renders the full HTML using frappe.get_print() with your chosen Print Format and sends it to this Windows app ready to print.

Troubleshooting

Issue	Solution
Connection failures	Check config.json URL and credentials
No printers detected	Verify printers are installed locally
PDF generation fails	Check wkhtmltopdf path and installation
Silent print fails	Check SumatraPDF path and printer name

Related Projects

• local_printers — Frappe app for ERPNext integration

License

MIT License