detect failure of rs232 communication in keil 'c' program

i want to detect failure of rs232 communication between 2 microcontrollers ,

So have you given some thought yet about what would constitute communication failure in your case? Or, to turn it around: how would you detect that communication has not failed?

please suggest me how to code in keil 'c' program

Not possible. You don't seem to be anywhere near the point where you (or anyone else) could start coding this. You haven't analyzed the problem enough to allow designing a solution, much less coding it.

i want to detect failure of rs232 communication between 2 microcontrollers ,

So have you given some thought yet about what would constitute communication failure in your case? Or, to turn it around: how would you detect that communication has not failed?

please suggest me how to code in keil 'c' program

Not possible. You don't seem to be anywhere near the point where you (or anyone else) could start coding this. You haven't analyzed the problem enough to allow designing a solution, much less coding it.