Interfacing of GSM modem with 8051 microcontroller

"modem is not responding properly"

In what way is it "not responding properly"?
What precisely is "improper" about it?

How have you confirmed that it's the modem that is not responding "properly", rather than your code that is not sending the commands properly, and/or not handling the responses properly?

Have you fully checked your hardware - is the baud rate corect? Are all the control signals correct? Is the cable good? Are the voltage levels correct?

"Can you send some details regarding this?"

Details of what, exactly?
You haven't even said what modem you're using, so how can anyone give you anything detailed without that basic knowledge?!

As I said before:

Have you read the Manual for your GSM modem?
Have you visited the manufacturer's website, and reviewed the available support materials - Application Notes, examples, reference designs, etc?

Have you run your code in the Keil Simulator, connected to your modem?

Again, You need to adopt a methodical approach to debugging this - take one step at a time, so that you know exactly what does and does not work.

"modem is not responding properly"

In what way is it "not responding properly"?
What precisely is "improper" about it?

How have you confirmed that it's the modem that is not responding "properly", rather than your code that is not sending the commands properly, and/or not handling the responses properly?

Have you fully checked your hardware - is the baud rate corect? Are all the control signals correct? Is the cable good? Are the voltage levels correct?

"Can you send some details regarding this?"

Details of what, exactly?
You haven't even said what modem you're using, so how can anyone give you anything detailed without that basic knowledge?!

As I said before:

Have you read the Manual for your GSM modem?
Have you visited the manufacturer's website, and reviewed the available support materials - Application Notes, examples, reference designs, etc?

Have you run your code in the Keil Simulator, connected to your modem?

Again, You need to adopt a methodical approach to debugging this - take one step at a time, so that you know exactly what does and does not work.

Thank you MR. Andy, as you said, modem(WAVECOM) is responding properly. The problem was improper handshaking signals. Now we are sending DTR and RTS signal to modem, for which it is responding properly. Thank you for your support.

Please can u send me the code what you have solved for the interface for 8051 with gsm modem because i am facing same problem what you has posted . please send tha code. this is for my college project purpose

"please send tha code. this is for my college project"

Surely the whole point of a college project is to demonstrate that you can solve the problem yourself?

After reading this thread, you should have sufficient information & resources to enable you to complete your project.

If you have specific questions, then ask them - but don't just cheat your course by copying someone else's work!

I agree with you Andy. How dare you to ask for the code?? Get up and do some work.