Hi all,


I have been working on an unique script of my own, which should be able to communicate with a classic 56kbit modem. I am quite a newbie to the scripting, but I suppose I am slowly making a progress.

At the beginning I had no idea how I was supposed to communicate with the modem. I am a Mac user (but I am using Debian as well) and I use the Terminal app mostly for everything and it works pretty fine, I'd say. For a physical connection with the modem I am using a USB-to-RS232 (serial port) adapter (AXAGO ADS-50) at /dev/cu.usbserial*.

For turning on the TR (terminal ready) signal I have already used a cat command followed by a ampersand to make it go to the background. At this point I mark a PID number to myself to kill it afterwards. (I am having some problems with a jobs implementation at the moment.)

To the modem I send AT commands using the echo command, eg. echo -n ATH^M > /dev/cu.usbserial*. (The ^M sing at the end is a combination of CTRL-V and CTRL-M characters.)

The script(s) itself works quite fine. It initialises the modem, makes it go offhook, even is able to make a genuine connection between two 56kbit modems. I can send text strings through the modems to each other and I am working on a simple script which can send (cat > device) simple text files.

And here comes the problem. Just today I have found out how to hang-up the modem, but since I process ATH0 to one modem and the other one hangs as well, the second modem also drops the cat > device process, the TR signal of this modem is still on and I cannot use it anymore untill reboot. I tried to kill that process with kill PID, but it cannot be found even in the ps ax list. If I kill the process before the dialling and making of connection, the TR signal successfully disappears.

I am stuck at this point and I have no idea, how could I make it work properly. I have realised that the second modem sends a EOF signal (^D) to the log before the cat process drops.

I would be glad for any help. Thank you and sorry for a long post and a poor level of my English.


- krustowski (krusty was not available already)