Running JAVA EE application on Tomcat server

I have JAVA EE web app, written and tested on Windows (I used Tomcat server). I also have remote access to VirtualBox Machine where Ubuntu 14.04 is installed. I'd like to be able to run my app on this server and have access to it from my browser. I've installed there JAVA 7 and Tomcat 7. I'm getting access to the server by Putty using IP address and 1522 port. I copied my .war file to this server by psftp and then I copied it to

 /var/lib/tomcat7/webapps

folder. I've checked what ports are open by this command:

>nc -zv IP_ADDRESS 80     
Connection to IP_ADDRESS 80 port [tcp/http] succeeded!

and I realized that 80 port is opened, so I've edited

/etc/tomcat7/server.xml

file and I changed port from 8080 to 80. After that I still can't connect to the server. I'm typing in my browser:

IP_ADDRESS:80

and I get 404 error. What am I doing wrong? I have firewall disabled so it's not that.

@EDIT: I'm starting Tomcat like that:

sudo service tomcat7 stop/start/restart