SMS Delivery Abnormalities

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IT Support
New member
Username: Nextcsl

Post Number: 1
Registered: 01-2016
Posted on Wednesday, January 27, 2016 - 10:55 am:   

We recently upgraded to v2015.06.24, since then we have noticed that we have been receiving inconsistent SMS messages. The SMSOUT.log shows the correct SMS that we should receive however the one physically received on the phone is different, it's mixed together with a different part of another SMS. This occurs for multi-part messages over the standard SMS length of 160 characters.
Des - NowSMS Support
Board Administrator
Username: Desosms

Post Number: 5559
Registered: 08-2008
Posted on Wednesday, January 27, 2016 - 05:23 pm:   

What type of SMSC connectivity?



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Des
NowSMS Support
IT Support
New member
Username: Nextcsl

Post Number: 2
Registered: 01-2016
Posted on Thursday, January 28, 2016 - 10:34 am:   

Hi Des, we are using a GSM modem that is accessible via a local COM port
Des - NowSMS Support
Board Administrator
Username: Desosms

Post Number: 5562
Registered: 08-2008
Posted on Friday, January 29, 2016 - 03:35 am:   

That is extremely bizarre. We haven't had any other similar reports, so I can't imagine what would cause this type of behavior.

How are the messages being submitted to NowSMS? HTTP, I assume? And the entire long message is submitted in one request?

We need to collect some info...enable the SMSDEBUG.LOG...and recreate the problem. I'd like to see the SMSDEBUG.LOG and SMSOUT.LOG for a time period in which the problem occurs, and detail of what was received on the phone...preferably a screen capture. Please provide detail of destination number and time.

Email this to nowsms@nowsms.com with Attention: Des on the subject line. Also post a quick reply here to remind me to look for the message if it does not get routed to me automatically.

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Des
NowSMS Support
IT Support
New member
Username: Nextcsl

Post Number: 3
Registered: 01-2016
Posted on Monday, February 01, 2016 - 02:31 pm:   

Hi Des, i have sent an email to nowsms with the logs.
Thanks,
Darren
Des - NowSMS Support
Board Administrator
Username: Desosms

Post Number: 5563
Registered: 08-2008
Posted on Monday, February 01, 2016 - 07:21 pm:   

Hi Darren,

I think I have a pretty good idea of what is occurring.

It is related to delivery reports.

The following sequence is frequently occurring:

Send Part 1 (AT+CMGS)
Confirm Sent Part 1 (+CMGS: ###)
Send Part 2 (AT+CMGS)
Delivery Report Part 1
Delivery Report Part 2 (unknown ID because missing confirm)
***TIMEOUT - Missing Confirm Sent Part 2 (+CMGS: ###)

Send Part 2 (AT+CMGS) *** DUPLICATE
Confirm Sent Part 2 (+CMGS: ###)


So essentially, the device receives part 2 twice, which is why some messages are mixed up.


The problem is that the modem seems to sometimes get confused if a delivery report arrives while another message is being sent. The modem sends the message, but never confirms, so NowSMS sends again.

Disabling delivery reports should provide a temporary fix.

But I am intrigued that you say the problem started after upgrading NowSMS. Was the previous version more than several years old, and were you using delivery reports?

I know that many modems don't provide delivery reports unless the modem is configured to push them to the app as they arrive. NowSMS will accept them via direct push, or poll for them.

A few years ago, we modified the modem init process to ask for delivery reports to be pushed. But when this push occurs, the modem sometimes gets confused if a send is in process.

So the solution might be to disable pushed delivery reports and allow NowSMS to poll for them.

To do this, edit SMSGW.INI, and under the [Modem - COM4:] header, add:

CommandPostInit1=AT+CNMI=2,1,1,2,0

This should tell the modem to store delivery reports and let NowSMS poll for them. After enabling this setting, and letting some more messages be sent,, send me another SMSDEBUG.LOG so that I can see the impact of that setting.

What model is the modem?

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Des
NowSMS Support
IT Support
New member
Username: Nextcsl

Post Number: 4
Registered: 01-2016
Posted on Wednesday, February 03, 2016 - 08:42 am:   

Hi Des,

The original config was NowSMS v2010.02.09 on windows 2000 with an Option Globetrotter 3G modem that was likely purchased around 2010.
What we are currently running to try and isolate the issue is the same NowSMS v2010.02.09 but on a Windows 2008 virtual server with the same Globetrotter modem so possibly the VMware virtualisation layer or OS is having an effect.

I have added in the config and restarted the service (I hope it's supported on that version) I will monitor for the next couple of hours and then post the logs.
IT Support
New member
Username: Nextcsl

Post Number: 5
Registered: 01-2016
Posted on Wednesday, February 03, 2016 - 02:45 pm:   

Des,

I have sent the debug log to nowsms email. As mentioned in the email the SMS’s are being received correctly so you are correct that is the issue. However we are now only sending 1 part of an SMS per minute with this disbaled, any further suggestions? We would be open to purchasing a new modem if that is more likely to work.

Thanks,

Darren

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