Akhil:

It is possible that the GSM device needs to see one of its input handshaking lines placed an an active level so as to enable the communications. Even though you had success with the HyperTerminal working when configured for no handshaking the output control lines on the port are most likely placed into the "active" level when HyperTerm makes the initial connection.

A second possibility is that maybe you wired the cable that you built incorrectly. I have to share with you that I cannot count the number of times I very very carefully built up a cable thinking I had it all counted and soldered correctly only to find that I had screwed up. So do check your own-built cable again. Also check carefully that one strand of wire from one terminal of the Dsub-9 connector did not accidentally sneak out of the solder cup on the back of the pin and short to the adjacent pin.

Michael Karas