@Rohan Panda , Thanks for posting this good question and closing the thread by sharing the solution that worked for you.
To benefit the community, I have re-opened the thread to share the solution you posted "I added a key called PORT in application setting and set it to value 3000 and the app is now working".
Just adding this document: Yes, the recommendation is to use app setting WEBSITES_PORT to set the port for your own docker image while for blessed images use PORT environment variable as the listening port.
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