by Abhishek Pawar.
Dear deva m,
U just need almost two file to start your web service.
1) db/service.php
2) externallib.php
service.php contain two array and externalib.php contains external functions.
just go through this url https://docs.moodle.org/dev/Adding_a_web_service_to_a_plugin#Quick_start
for more information : https://github.com/moodlehq/sample-ws-clients
Best Regards,
Abhishek