I've set up virtual COM ports with com0com (COM20 and COM21), but I'm having trouble accessing them through Python's pyserial.

What I've tried

I can successfully create the port pair using com0com's setupc.exe:

> setupc.exe install PortName=COM20 PortName=COM21

The virtual port pair is visible in the com0com GUI:

and they appear under com0com - serial port emulators in device manager:

But when I try to access these ports with pyserial, I get a FileNotFoundError:

import serial
import serial.tools.list_ports

# List available ports
print("Available COM ports:")
for port in serial.tools.list_portsports():
    print(f"  {port.device}: {port.description}")

# Try to open the virtual port
try:
    ser = serial.Serial('COM20', 9600, timeout=1)
    print("Successfully opened COM20")
    ser.close()
except Exception as e:
    print(f"Error: {e}")

Output:

Available COM ports:
  COM7: Standard Serial over Bluetooth link (COM7)
  COM3: Intel(R) Active Management Technology - SOL (COM3)
  COM6: Standard Serial over Bluetooth link (COM6)
Error: could not open port 'COM20': FileNotFoundError(2, 'The system cannot find the file specified.', None, 2)

Environment

• Windows 10
• Python 3.12.2
• pyserial 3.5
• com0com 3.0.0.0
• Running script with administrator privileges

Questions

1. Why aren't the com0com virtual ports appearing in the pyserial port list?
2. How can I make pyserial recognize and use com0com virtual ports?
3. Is there a delay or extra step needed after creating ports before they're accessible?

I've already tried:

• Running as administrator
• Creating ports with higher numbers (COM20, COM21)
• Verifying the ports in Device Manager and com0com GUI
• Restarting the computer

Any insights or alternative approaches would be greatly appreciated.