I need to send some commands from a computer via GPRS protocol to some devices.

The options I have found so far are:

Is there any limitation if i use the Arduino or an old phone?

Or should I buy the "real" modem?

I need the solution to be very reliable.

PD, if this is not the right place on stackExchange, please let me know where to post it. Cheers

  • \$\begingroup\$ Most important information is missing: how reliable you need this to work? \$\endgroup\$ – Rokta Mar 27 '19 at 10:08
  • \$\begingroup\$ hi @Rokta thanks, edit done, I need it to be very reliable \$\endgroup\$ – manuelBetancurt Mar 27 '19 at 10:10

If you want (or need) reliability, then you should stick with a commercial modem.

If you use an Arduino with a modem module, then you will end up writing software for the Arduino and for your computer. That makes for more opportunities for problems and program errors.

Use a commercial module, and you only have to write software for the computer.

This is right up my alley.

The company I work for has as a (small) part of a larger system an interface to GSM modems to send SMS messages. This thing has to run 24/7 365.

Reliability isn't just a question of hardware. It is as much (maybe more) a question of the software.

Your software needs to be aware of and capable of dealing with a lot of error conditions.

What do you do when the modem has no connection to the net?

What do you do when somebody forgot to pay the bill and the SMS can't be sent?

What do you do when some yoyo uses a pre-paid SIM, and it runs out?

What do you do when despite using good hardware, the modem does a restart in the middle of sending an SMS?

When we wrote ours, it was assumed it would be trivial (by people who aren't programmers) because sending an SMS is such a trivial, everyday thing to do.

It ended up taking several weeks, 90 percent of which was devoted to handling errors that the GSM modem produces.

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  • \$\begingroup\$ @Mako: I tend to stay on the site. If you need information about a particular detail, ask here in the comments. Whatever it is might be worth asking in a seperate question or it might be better as an addition to this question and answer. \$\endgroup\$ – JRE Mar 27 '19 at 11:53
  • \$\begingroup\$ Ok cool, so I will get a proper modem, I have seen some with multiple antennas, Why?... I mean if I send some messages they will go on a queue or parallel? will the modem handle ok multiple incoming requests with one antenna? Thanks! \$\endgroup\$ – manuelBetancurt Mar 27 '19 at 11:57
  • \$\begingroup\$ Is there an opensource "server" that is compatible with most modems? thanks \$\endgroup\$ – manuelBetancurt Mar 27 '19 at 12:11
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    \$\begingroup\$ Multiple antennas are normally used to improve the radio signal. You don't receive SMS over multiple antennas at the same time. Messages are usually sent one after another. You can put them in a queue in the modem, and then monitor the status - the modem will send them sequentially. Some modems will spontaneously tell you when you've received a message, but most don't. You are better off periodically asking the modem if it has received any messages. \$\endgroup\$ – JRE Mar 27 '19 at 12:14
  • \$\begingroup\$ I don't know about any kind of open source "server" for sending/receiving SMS. \$\endgroup\$ – JRE Mar 27 '19 at 12:15

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