Re: SMS sending error with Telit module

[Dan Williams <dcbw redhat com>]

On Mon, 2013-04-08 at 10:39 +0200, Enrico Murador - Research &
Development - CET wrote:
> I'm trying the packages I updated friday from PPA, but now I'm facing 
> another problem: after I start the gsm data connection, most of the time 
> connection drops automatically... sometimes immediately after 
> connection, sometimes after some seconds (and in the meantime, I see the 
> modem status icon on top right of the screen in "searching" state). 
> After the connection drops, the modem seems to become "unreachable" from 
> the manager. I can get it working by disconnect and reconnect the 
> module's USB cable, without powering it off.
>
> Side effect: one time, after some retries, I was able to completely 
> "lock" the applet with both LAN and mobile connections disabled, and 
> clicking on the connection names didn't make any effect, apart from this 
> message repeatedly popping up: "(4) Did not receive a reply. Possible 
> causes include: the remote application did not send a reply, the message 
> bus security policy blocked the reply, the reply timeout expired, or the 
> network connection was broken.".
>
> Attached is the log of a failed attempt, where connection drops (line 
> 755) some seconds after going up, and subsequent (failed?) attempts to 
> check module's state.
> Is there a way to show in log also the cause of the disconnection?

If NetworkManager is being used here, what does the PPP exchange look
like?  Does ppp0 get an IP address from pppd before the disconnection,
or does the PPP negotiation just fail?  You'll see that wherever syslog
gets dumped to, sometimes /var/log/messages,
sometimes /var/log/daemon.log, etc.  Clearly the modem isn't completely
wedged because the QCDM port still works.  But getting the pppd output
might help diagnose.

Some theories are:

1) double-check the APN

2) perhaps PPP fails for some reason, but when pppd quits on the local
machine the module doesn't actually leave data mode; we don't have
multiple AT ports so there's no way to force the device to leave data
mode with AT+CGACT.  The device might require other mechanisms like
serial HUP or dropping DTR or +++.

Dan