How are you supposed to programatically detect when the remote modem on your call hangs up? I am writing a C program which interfaces with a SoftModem device
/dev/ttySL0 in Ubuntu linux. I am able to configure the modem using Hayes AT commands and communicate with the remote modem. However, I haven't been able to determine how I'm supposed to detect that the other end has hung up the line.
I have the modem configured so that when the other end hangs up, the device prints
NO CARRIER and switches to command mode. However, I can't use the
NO CARRIER string because I can't guarantee that the modem won't receive that string while in data mode.
How do you "listen" for remote hang up?