can any one help me with the code for the gsm modem interfacing with 8051
The OK just indicates that the AT Command was accepted by the modem - it does not indicate succesful transmission of the message!
The message is not confirmed as sent until you subsequently receive the Message Reference (MR) number.
But the OP's project is receiving the message - not sending it.
You do realise, don't you, that there are dozens - possibly even hundreds - of projects already published on the internet which do exactly this?
Did you spend any time researching prior art?
www.lmgtfy.com
i tried it but am not able to get any code
Oh dear - so you might actually have to get down and write some of your own, then...?!