Transmit data on voice call's data channel on android

Question

When I worked low level with GSM modem it was possible to transmit data during the voice call through data channel (some info here https://en.wikipedia.org/wiki/GSM). So, for example, with the help of the AT commands to the gsm modem I could send the "1" and on the other side to get the "1". The flow was: 1. Dial number. 2 Transmit data. I remember that I've even written my own ppp->icmp/ip->udp stack on the assembler. so my device was able to communicate through this gsm-modem with internet service providers. (Also it was possible to talk if to connect the mic and headphones to the gsm modem and transmit data at the same time.) The question is how to do similar in android. Is it possible to transmit data over this data channel with the help of the android API?

Answer 1

As far I know you can't do that in the Android. Simply you can't modify programmatically a call in any way. The API won't allow it. That's why we don't have any working answering machine apps on the market.