Hi Mike,

On 05/26/2015 10:38 AM, Mike Williams wrote:
> All,
>
> Using connman/ofono to connect to a cellular network, the first time
> activating the GPRS context works. After deactivation, the next
> activation fails with an unknown error. I believe this is related to
> this issue:
> https://lists.01.org/pipermail/ofono/2015-May/015745.html
>
> Looking through the code, it looks like at_gprs_activate_primary() fails at:
>
>         if (g_at_chat_send(gcd->chat, buf, none_prefix,
>                                 at_cgdcont_cb, gc, NULL) > 0)
>                 return;
>
> g_at_chat_send() is returning NULL from at_chat_send_common() because
> the chat command_queue is NULL.

That generally happens because the underlying AT command port for the 
GAtChat has been closed (most likely due to a serial line hangup).

What modem are you using?  Some manufacturers' modems are known to have 
this issue: whenever the PPP connection is dropped, the AT command port 
is closed by the modem.  Issuing AT&C0 should disable this behavior, but 
some modems do not honor that command.

Regards,
-Denis