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As far I have informed around the net after hours of research it is not possible to receive/sending SMS while there is a open GPRS connection. Am I right or wrong ?

I am currently developing an application which purpose is to have an open GPRS connection to send data from when it receives an SMS. Is it possible somehow to keep the connection open and receive SMS's while the GPRS is active, or do I have to close the GPRS connection on the computer every time I want to check if I have received an SMS?

I am using an 3G modem for the purpose. I am handling the SMS from a C application, and the GPRS connection is handled by the OS (Ubuntu).

BenMorel
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user1188650
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1 Answers1

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A lot of modems are capable of multiplexing. So one channel is for standard AT commands and then a dedicated channel for GPRS/UMTS communication. Is your modem capable of that?

UPDATE

Possibly this may help you. I have used a variant of this multiplexer to have multiple channels running for AT commands.

Matt Aldridge
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  • When I plug it in there is two channels attached to each serialport. – user1188650 Feb 04 '12 at 09:58
  • Sorry, too early posting (pressed enter). It is an Hueawei E122. The problem is that when I open the connection from Networkmanager in Ubuntu or another dialer, it locks the device completely so I can't reach it from my program. – user1188650 Feb 04 '12 at 09:59
  • I know with other modem types you must connect via the AT command interface and configure them to properly multiplex. Do you have a developer manual for the modem? – Matt Aldridge Feb 04 '12 at 10:05
  • This modem also needs to connect via AT commands, but unfortunately I can't find any developer manual or anything similar. It is just a standard 3G modem device from a teleprovider. – user1188650 Feb 04 '12 at 10:36
  • But I guess if you setup multiplexing via AT commands, the same will work on this one. Otherwise I just have to get out and buy a modem which usage is for developing. – user1188650 Feb 04 '12 at 10:36
  • I had a look for some manuals but it doesn't seem like they publicize them. I know for Sierra Wireless they are a little guarded and tend to only give out the manual to people that write the drivers. AT+CMUX? should confirm if the function is available .. and AT+CMUX=? should give you the available options usually. – Matt Aldridge Feb 04 '12 at 14:09
  • Yes they are very hard to find. But from your posts about the multiplexing I managed to find some guides how to use CMUX and the multiplexing in the modems. So what I am going to do now is to buy a new modem that supports CMUX and then install virtualdrivers so both the application host and the GSM modem supports multiplexing. That way I am hoping to be able to use the GPRS connection and AT commands at once. Do you know if a virtualport driver like 'socat' is supporting the multiplexing protocol or if I have to use GSMMUX which you refered to? – user1188650 Feb 04 '12 at 15:57
  • Yes you would specifically have to use GSMMUX because there is a standardized interface for all GSM modems (GSM 07.10). Are you only able to use external modems? – Matt Aldridge Feb 04 '12 at 16:45
  • I kind thought that as well. Yes the modem will be attached to a SingleBoardComputer. So either I have to use GSMMUX or buy a SingleBoardComputer that allows a GSM board to be attached to. Thank you so much for your help, I really appreciate it! – user1188650 Feb 04 '12 at 17:17
  • Some modems offer you the possibility of having a GPRS (data) connection while being able to receive SMS. Using command mode and unsolicited messages (SRING, +CMT) you can be notified when data is coming or an SMS arrived. I'm referring to Telit devices, which have this option. – INS Feb 06 '12 at 12:59
  • Thanks. I guess I have to buy myself a new modem that supports all this before I continue the project :) – user1188650 Feb 12 '12 at 11:12