Twisted's Serialport and disappearing serial port devices

Question

Hi,

I'm using twisted.internet.serialport to have my program be continuously connected to a device on a serial port.

Unfortunately my serial port is just a usb device, which means it can be disconnected or reset by the OS at any time (port 2 disabled by hub (EMI?), re-enabling... ). I see that pyserial has support for this for a few weeks and raises a SerialException.

What I would love to do is try to reconnect to the serial port that just disappeared every few seconds.

So, is there any way how I can tell twisted to notify me about a disconnect? Or should I go ahead and write a threaded wrapper for pyserial?

Thanks

Answer 1

http://twistedmatrix.com/trac/ticket/3690 may be related. The ticket appears blocked on proper Windows support. I'm not sure if this kind of disconnect event will trigger Twisted's internal connection lost detection code, but I would expect it to (even without a recent version of pyserial). You could probably try out the branch linked from that ticket pretty easily to see if it does what you want, at least. And if so, perhaps you could help get the ticket actually resolved (the 10.2 release is coming up pretty soon, wink wink nudge nudge).

Answer 2

It seems the only relevant change in branched version is a call to connectionLost() in the protocol.

Until it's fixed in the trunk I use a:

class fixedSerialPort(SerialPort):
    def connectionLost(self, reason):
        SerialPort.connectionLost(self, reason)
        self.protocol.connectionLost(reason)

I tested it with Twisted 10.1 (on ubuntu) and 8.1 (on my trusty debian). Both works fine. No idea about other OSs though.