I'm wondering what's needed (back-end-wise) to send an SMS message? Is this what SMS Gateway software does?
I'm looking at examples like this:
but I don't understand where the 'magic' of sending the SMS to a user's phone happens. If I have a test phone number, like 1-555-555-5555 - what do I actually need to get an SMS sent to that device? I know each platform has services you can use to do that (like iPhone, Android etc) but that goes through the user's carrier. I'm interested in handling sending the SMS messages myself (if possible)