Hi Shreyas A,
this is most probably caused by port 8080 is already in use so the Default JBOSS AS 7 that comes with the installer cannot start there.
Try to confirm that there is no other process using port 8080 before running "ant start.demo"
tips: if you are using Windows, you can go to cmd and use "netstat -aon" to get the list of port being used and also its processId.
Regards,
Thomas Setiabudi