Re: Feature request/wish for Kannel

This mail will be slightly off topic, but I need to comment on the issue 
the author has already recognized :)

Yes, that issue when everything looks "fine" - but you need to restart 
Kannel to get SMSes in masses - is something that I've been struggling 
for few months in the spring of 2006.

I solved the problem (tested on the Siemens family of GSM modems), and 
happily use my version of Kannel since. I presented the first part of 
the solution somewhere at the end of May 2006, but got no response - so 
I gave up committing to devel-kannel (since my sole concern is smsc_at).

Long story short, the problem is in forcing the modem to send an SMS - 
even if it reports an error.

In the official Kannel version, there is a RETRY_SEND (equal to 3, in 
smsc_at.h) define that defines how many times an SMS sending process 
needs to be retried. It's  purpose is illogical - having a complete and 
logical sms-resend-retry mechanism built in the Kannel logic.

In the official Kannel version, if the software receives an error 
response while trying to send the SMS, it simply tries again in a loop 
(3 times, due to the value of RETRY_SEND). Such a behavior confuses the 
GSM modem - on the first forcible SMS sending retry.

If the software should report unsuccessful SMS sending through
 bb_smscconn_send_failed(privdata->conn, msg, 
SMSCCONN_FAILED_TEMPORARILY, octstr_create("ERROR"));

and let the modem "relax" (by asking it if there are new incoming SMS 
messages pending) when it receives an error response from the modem, I 
have seen that Siemens modems (TC 45, MC 39i) would never expose the 
notorious issue.

I have never encountered the issue in the last 15 months - since I 
altered the logic within smsc_at.c. With the RETRY_SEND mechanism, I 
have had the issue more than once daily (I operate the GSM modems in a 
rather intense SMS traffic).

Hope this comment will lead to a usable official version of smsc_at.c in 
the future.

Best regards,
Andrija Petrovic

Andreas Fink wrote:
> this is kinda dangerous as the at command and response are in a tight 
> loop.
> you could very easily screw up kannel. 
>
> For example you set echo off/on and kannel would get confused.
> The problem you are seeing is usually not related to information the 
> operator sends which get reflected into AT commands.
>
> But I have seen similar issues where everything looks "fine" but SMS 
> just dont hit the phone. After restarting kannel, the queued SMS come 
> in in masses.
>
> My approach to this problem would be to use the kannel keepalive 
> mechanism not only to send a AT and wait for Ok but to go through the 
> initialization sequence again.
>
>
> On 05.09.2007, at 11:39, Nis - Kannel wrote:
>
>> This seems the only maillist for contacting the developers behind Kannel.
>> If not, please tell me how or where.
>>
>> I have been using Kannel for some time now and not had any problemes 
>> since i got it running.
>> The troubles that i get, is releated to the modem/mobile devices.
>>
>> So my request/wish is a Kannel utility for sending AT commands to the 
>> modem/mobile devices.
>> Some of the mobile companies, likes to send new settings or clock 
>> adjustments without warning.
>> And after one of those, the mobile no longer working without 
>> restarting Kannel.
>> Some mobiles just cant clear the stored sms and runs out of space.
>> If a SIM card i failing, it can take days before it's noticed.
>> Or any othter things that can be monitored by using AT commands and 
>> thereby prevented.
>>
>> Since Kannel locks the connection, other programs can't access the 
>> device.
>> Could it not be possible to make somekind of pipe through Kannel, so 
>> someone can inject AT commands and get the reply from the device?
>> Then someone can make there own scripts for sending and reading AT 
>> commands.
>>
>> Any reply related is much appreciated.
>>
>> /Nis 
>
>
>
>
>
> Andreas Fink
>
> Fink Consulting GmbH
> Global Networks Schweiz AG
> BebbiCell AG
>
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