Hi, I have finished the neat version of using the SerialPort in Win32. Without the bothering loseConnection tracebacks. First of all, I have to apology for the mistake in my last post. I claimed that calling the flashInput and flashOutput can be used as the workaround.I am wrong. The way I use with SerialPort is different from the standard way: SerialPort(protocol_instance, comport, reactor, baudrate) instead, I create a SerialConnect and connect the serial port by: connector = reactor.connectWith(SerialConnector,comport,baudrate,factory) I welcome someone else to improve this connector for it to be more reliable if this approach is worthy. For the script, please see the attachment. Iap BTW: I am not sure if it is proper to attach the script in mail list. I tried to paste it in the mail body. After pasting it into the gmail's editor, the format of the script is terrible.