What did I do wrong when building receiver with pyserial?

Question

I am using XBee modem to make mutual remote communication system.

Initially I tried using Arduino, however, I figured out that using two single board computer with python would be much more convenient. I am using pyserial right now.

This is the code which I made. It is really simple, and I don't see there would be something cause error.

Transmitter

import serial
import time
Xserial=serial.Serial('COM4',9600)

for i in range(10):
    print(i)
    Xserial.write(b"Test2")
    time.sleep(3)
Xserial.close()

Receiver

import serial
import time
XSerial=serial.Serial('COM10',9600)
while (True):
    line=XSerial.read(1)
    print(line)
XSerial.close()

I think transmitter is working, however, receiver does not seem to receive what I send.

I am sure that it was working yesterday, but it is not working today. I checked XCTU and the connection is fine. I can communicate with each other by XCTU.