back end server is not writing data to serial port

Question

I'm building a webpage to control my home automation system (Teletask) It's an older system which still uses a serial interface. I have a pc running to control other stuff and this pc runs 24/7 I hooked it up to the home automation system and I can control it with a webpage running locally. I installed node.js; created a project folder, did a npm init and install express created a server.js file (see below) front end is talking to back end but nothing is shown on the serial port (monitored with Serial Port Monitor)

relevant code front end look like this:

<script>
 async function sendToSerial(hexCode) {
 try {
 const response = await fetch('http://localhost:3000/sendToSerial', {
  method: 'POST',
  headers: {
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({ hexCode }),
});

if (!response.ok) {
  throw new Error(`Request failed with status: ${response.status}`);
}

const data = await response.json();
console.log('Server response:', data);
 } catch (error) {
    console.error('Error during serial communication:', error.message);
}

}

back end code looks like this:

async function sendToSerial(hexCode) {
 console.log('Sending to serial port:', hexCode);

const port = new SerialPort('COM3', { baudRate: 19200 });

return new Promise((resolve, reject) => {
port.on('error', (err) => {
  console.error('Serial port error:', err);
  reject(err);
});

port.on('open', async () => {
  console.log('Serial port opened successfully.');
  
  try {
    const data = Buffer.from(hexCode.replace(/0x/g, ''), 'hex');
    await port.write(data);
    await port.drain();
    console.log('Data sent successfully.');
    resolve();
  } catch (error) {
    console.error('Error during serial communication:', error);
    reject(error);
  } finally {
    if (port.isOpen) {
      await port.close();
      console.log('Serial port closed.');
    }
     }
    });
  });
}
 const PORT = 3000;
 app.listen(PORT, () => {
  console.log(`Server is running at http://localhost:${PORT}`);
});

`

when running:

C:\inetpub\wwwroot\teletask>node server.js Server is running at http://localhost:3000 Sending to serial port: 0x02,0x07,0x01,0x01,0x08,0xff,0x00,0x12 Sending to serial port: 0x02,0x07,0x01,0x01,0x08,0xff,0x00,0x12 Sending to serial port: 0x02,0x07,0x01,0x01,0x08,0xff,0x00,0x12 Sending to serial port: 0x02,0x07,0x01,0x01,0x08,0xff,0x00,0x12 Sending to serial port: 0x02,0x07,0x01,0x01,0x08,0xff,0x00,0x12

codes are seen but not sent to serial port. Yes it's the correct one and yes I can send via serial port monitor commands using this port.

Can you shine your light on this one? :) Much appreciated