BillBook Printer Helper v0.3

Security & Token Setup

Starting with v0.3, the helper only accepts requests from the local machine and requires a valid X-Print-Token header. The same token must be configured in both the helper and your server.

1. Generate a strong random token and set PRINTER_HELPER_TOKEN in your server's .env file.
2. Compile the helper with the same token in the ExpectedPrintToken constant.
3. Expose the token to your frontend (e.g. window.PRINT_TOKEN or window.POS_CONFIG.print_token).
4. Send 'X-Print-Token': yourToken in every fetch to localhost:9100.
5. Add http://localhost:9100 to your CSP connect-src directive.

The helper binds to the loopback interface only, so remote machines cannot connect even if port 9100 is reachable.

1. Fetch Connected Printers (GET `/printers`)

Retrieve a JSON array of all printers installed on the client's Windows machine:

fetch('http://localhost:9100/printers', {
  headers: { 'X-Print-Token': (window.PRINT_TOKEN || '') }
})
  .then(res => res.json())
  .then(printers => {
    console.log("Installed printers:", printers);
  })
  .catch(err => console.error("Helper is not running", err));

2. Direct Silent Printing (POST `/print`)

Send a print job directly to a specific printer without opening any browser dialogs. The body must be a JSON object containing the printer name and the absolute URL of the PDF:

fetch('http://localhost:9100/print', {
  method: 'POST',
  headers: {
    'Content-Type': 'application/json',
    'X-Print-Token': (window.PRINT_TOKEN || '')
  },
  body: JSON.stringify({
    printer: 'XP-80', // Replace with the selected printer name
    url: 'https://example.com/invoices/bill-101.pdf' // Absolute PDF URL
  })
})
  .then(res => res.json())
  .then(data => {
    if (data.status === 'success') {
      console.log("Printed successfully!");
    } else {
      console.error("Print failed:", data.message);
    }
  })
  .catch(err => console.error("Network error connecting to helper", err));