mart256:
how do you program in Unix. Are there compilers and IDE to do so? Or just a Linux distro.
There are compilers of course. And IDEs. You can use any of a dozen Linux distributions, Free/Net/OpenBSD, Solaris -- take your pick.
My point was only that if the private network involves a proper computer -- as opposed to a microcontroller like a AVR Arduino -- that might be a good place to implement an ethernet/SMS gateway -- rather than trying to cram this function into an Arduino.
Btw, maybe its easier to program in Arduino than Unix.
By some measures yes, by others, no. If you are used to programming real computers, then programming them is easier than the Arduino. If you've never programmed anything for any purpose before in your life, then getting started with Arduino is less daunting than picking up a PHP, SQL and C/C++ manual.