Hi @Tejas Morkar ,
App Service looks for a listening port to bind to, so it knows where to forward the web requests. It looks to me that a continuous web job would be better fit to run your node app. See https://learn.microsoft.com/en-us/azure/app-service/webjobs-create and https://github.com/projectkudu/kudu/wiki/WebJobs for more details.
If you run into issues or need any further clarification, please feel free to comment down below.
Regards,
Ryan