The pySim-smpp2sim.py program exposes two interfaces:
* SMPP server-side port, so external programs can rx/tx SMS
* APDU interface towards the SIM card
It therefore emulates the SMSC, Core Network, RAND and UE parts
that would normally be encountered in an OTA setup.
Change-Id: Ie5bae9d823bca6f6c658bd455303f63bace2258c