First, I just want to see it is not a security group setup in ec2 console. because I can set up the apache, which is by fault 80 port and is able to visit the apache website through 80 port. but for tomcat, it works if I use port 8080(by default) or some values bigger than 1023(i think this port). but when I change server.xml(changing 8080 to 80) it cannot work if I use 80 port, I start the service successfully, but there is no 80/http listening. I know it should be some privileges issues(only the root can start service below 1023 port). but I did not know how to do it.