HTTP 405 Method Not Allowed及CORS问题求助（EPSON TM U220）

Got it, let's break down what's happening and tackle this step-by-step—since you can't modify the printer's firmware, we'll focus on changes you can make to your code or deployment setup.

First, Understand the Root Causes #

From your error details:

1. Origin: null means you're opening your HTML file directly via file:// protocol, which browsers treat as an extra-restrictive case for CORS.
2. The OPTIONS pre-flight request is getting a 405 because the printer's CGI endpoint only allows GET/HEAD/POST methods. Browsers send this pre-flight automatically when your request uses non-simple headers (like soapaction or custom Content-Type), which the Epson SDK relies on for HTTP-based requests.

Solution 1: Use the Epson SDK's WebSocket Connection (Not Direct CGI Calls) #

The ePOS SDK is designed to use WebSocket (port 8008) by default, which avoids CORS issues entirely—WebSocket connections don’t trigger browser pre-flight requests the same way HTTP does. Make sure you’re using the official SDK API instead of manually calling the service.cgi endpoint:

// Initialize the device with WebSocket port (8008)
const printer = new epson.ePOSDevice();

// Connect to the printer's WebSocket service
printer.connect('192.168.199.15', 8008, (connectionResult) => {
  if (connectionResult === 'OK') {
    // Open the printer device (use 'local_printer' as devid)
    printer.openPrinter('local_printer', (openResult) => {
      if (openResult === 'OK') {
        // Example print job
        printer.addText('Test print from JavaScript!\n');
        printer.addCut();
        printer.send((sendResult) => {
          console.log(sendResult === 'OK' ? 'Print successful!' : 'Print failed');
          // Clean up connection
          printer.closePrinter();
          printer.disconnect();
        });
      } else {
        console.error('Failed to open printer:', openResult);
      }
    });
  } else {
    console.error('Failed to connect:', connectionResult);
  }
});

Double-check that your printer has WebSocket enabled (most TM U220 models do by default). You can verify by visiting http://192.168.199.15:8008 in your browser—you should see a socket.io welcome response.

Solution 2: Host Your Code on a Local HTTP Server #

If you're opening your HTML file directly (file://), switch to hosting it on a simple local server to fix the Origin: null problem:

• Python: Run this in your project folder:

  # Python 3
  python -m http.server 8080
  # Python 2
  python -m SimpleHTTPServer 8080
  

• Node.js: Install http-server globally first:

  npm install -g http-server
  http-server -p 8080
  

Then access your app via http://localhost:8080/your-file.html—this gives you a valid Origin value, which plays nicer with the printer's security rules.

Solution 3: Package Your App as a Desktop Application (Bypass Browser CORS) #

If WebSocket isn't working and you still hit CORS blocks, package your JavaScript app into a desktop app using tools like Electron. Desktop apps don't enforce browser CORS restrictions:

1. Set up a basic Electron project, then add this to your main process file (main.js):

const { app, BrowserWindow } = require('electron');

function createMainWindow() {
  const win = new BrowserWindow({
    width: 600,
    height: 400,
    webPreferences: {
      webSecurity: false, // Disable CORS checks
      contextIsolation: false, // To access SDK in renderer process
      nodeIntegration: true
    }
  });
  win.loadFile('index.html'); // Your app's HTML file
}

app.whenReady().then(createMainWindow);

2. Run the app with electron .—this will let your code communicate with the printer without CORS errors.

Solution 4: Verify Printer Settings #

Quick check to rule out printer-side configuration issues:

• Log into the printer's web admin panel at http://192.168.199.15 (default credentials are usually admin/admin or blank)
• Ensure "ePOS SDK Settings" are enabled, and WebSocket port 8008 is open
• Confirm the printer is on the same network as your device

内容的提问来源于stack exchange，提问作者Raj