import serial

ups_port = "/dev/ttyUSB1"
usb_fake = "/dev/ttyUSBf"

ups = serial.Serial(port=ups_port, baudrate=2400, parity="N", bytesize=8, stopbits=1)
vp = serial.Serial(port=usb_fake, baudrate=2400, parity="N", bytesize=8, stopbits=1)

while True:
    vp_request = vp.read_until(b'\r')
    print(f'VP req: {vp_request.decode('ascii').strip()}')
    ups.write(vp_request)
    ups.flush()
    ups_response = ups.read_until(b'\r')
    print(f'UPS resp: {ups_response.decode('ascii').strip()}')
    vp.write(ups_response)