How to recover from serial device being force closed.

Aleksander Morgado aleksandermj at
Wed May 3 13:32:02 UTC 2023


> it would be great if you could verify the behavior on the main branch
> (at least on the last stable 1.20.6), and give us some logs, so we can
> have a better idea of the issue and how proceed, whether in a general
> manner, or with some specific fixes.

Yes, especially since several bugfixes were done that could help solve
the problem (although not sure if they were done in 1.20 or earlier

> >
> > I have encountered an issue while running ModemManager (version 1.18.4) on a Cinterion PLAS8 modem. Sometimes, the serial device used for AT communication with the modem is force closed (due to G_IO_HUP) without any obvious reason.
> >

Also, are you using NetworkManager along with ModemManager? Or are you
running pppd yourself? You must ensure that MM only touches the port
once pppd has exited, otherwise they'll use mismatched CLOCAL flags
and MM may get a HUP when the modem got disconnected from the network
(as opposed to getting a HUP only when the port goes away from the


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