How to use Android modem without using PC I have rooted my mobile. I wanted to use modem of Android phone without connecting to PC. How to give AT commands without connecting to PC, because in http://atinout.sourceforge.net/, it is suggesting to use '/dev/ttyACM0' file which is not present in Android device. 
I am not sure, but it seems ttyACM0 is related with USB, how to use same command in Android mobile, if I have rooted my mobile successfully.
Some devices would have the kernel compiled with ACM serial support (this is dependent on manufacturer/board/kernel) so that it could be used as a dial-up modem from a PC via USB cable, that is the functionality behind /dev/ttyACM n where n is a digit as allocated by the kernel.

To check for that, look in /proc/config.gz which is the kernel configuration file used, this is a gzipped file detailing the configuration of how the kernel was built, the ones you are looking for is, need to search for it:


CONFIG_USB_ANDROID_ACM=y
CONFIG_USB_F_SERIAL=y
CONFIG_MODEM_SUPPORT=y


again, its dependent, some elect to not include it, others will omit it

So basing my comment above, I think you're using the wrong device file name, the real modem device file is /dev/smd0 which is used in conjunction with /dev/socket/rild (See my answer on StackOverflow explaining about that). 
/dev/smd0 sits in front of /dev/socket/rild, rild daemon reads from that device and relays it to /dev/socket/rild which is then handled by the android layer in both directions.

Try using either of the device filenames, with atinout program referenced on sourceforge, to see what outcome you will get.

Disclaimer: I am not responsible for messing up your telephony stuff if you carry it out as per on the sourceforge site, if it gets messed, reboot!