Implementing a GSM Modem for SMS [closed]

Question

So I've got a website that serves ~1000 users, coordinating scheduling for events. I'd like to enable our system to send SMS messages to users. I have access to the server and would like to purchase and install a GSM modem instead of subscribing to some SMS Gateway service. What I gather so far is that I need to purchase the modem, and obviously a SIM card for that modem, and then a subscription for that SIM card.

Question 1 probably shouldn't go in StackOverflow, but I'll ask just in case... Do cellular service providers usually have unique subscription plans for companies or organizations sending bulk SMS messages?

Question 2: What kind of software is needed for GSM modems? How does one access the modem? Our server is a conventional LAMP architecture, site written in PHP. So... forgive me... but... how would I utilize the GSM modem? Options? Best practice?

Edit Some other posts link to this post, why does it not include a GSM modem? Or am I reading this wrong.

Edit This post refers to SMS Aggregators. What are they and where do they fit within the modem or gateway decision? Edit Oh. Just another word for SMS Gateway.

Answer 1

While I have read lots of opinions not to use simple GSM Phones to send bulk SMS, I have implemented a couple of these systems and have found them to be working quite well, as long as you follow some simple rules:

• Use lots of phones - we typically have 2-8 per server depending on the volume of SMS. Yes the phones will crash some times, we have seen a simple SE (Don't know the model right now, I think it was a K310i) running for years, and we have seen others crash more than once a month. By using more than one phone and a combined queue, a dead phone will reduce your SMS bandwidth, but will not stall the gateway.
• Ofcourse you can do some least-cost routing in the dequeueing process (Think doifferent carriers for the different phones), but be sure to not introduce a SPOF
• If possible make sure all phones have a known-good unbranded firmware - some provider-branded firmware versions will do strange things with SMS
• Before designing the system, think about deployment: It won't be easy to deploy GSM hardware in a data center. This can be a show-stopper.

Caveat: All the projects have been in Europe. Things might be different elsewhere, especial in the legal department. European carrier TOS tend to be friendlier to subscribers.

Answer 2

Nobody sending bulk messages does so with a GSM modem. For anything beyond a few messages here and there, you should be using an SMS gateway. Otherwise, you are limited to sending one message a time, bandwidth is very limited, and your provider won't like you very much. In fact, bulk sending is usually against the ToS (at least on CDMA providers here in the USA).

If you still want to go with this route, all you need is a way to open a serial port in PHP. Depending on your platform, this is relatively easy to do: http://code.google.com/p/php-serial/

If you need to do this on Windows, I recommend instantiating the .NET Serial class with PHP. See Serial comm with PHP on Windows for alternatives.

From there, all you need to do is send the appropriate commands. These sometimes vary from modem to modem, but you can find the more standard commands here: http://www.smssolutions.net/tutorials/gsm/sendsmsat/