I hosted a Python/Flask web service on my Amazon (AWS) EC2 instance.  modified the security group rules such that All inbound traffic is allowed. 
I can login from ssh and ping(with public ip) is working fine but I couldn't open the service URL from the web browser. Could any one please suggest how can I debug this issue?
Thanks,
It seems that web service isn't up and running or it is not listening on right port or it is listening just on 127.0.0.1 address. Check it with 'sudo netstat -tnlp' command. You should see process name, what IP and port it is listening on.
Web service hosted on EC2 host is not reachable from browser