Use Host Names Instead of IP Addresses – Home Network Guide

You need to create aliases of you network interface.

You have two options for doing this.

1. one is to create temporary aliases using ifconfig command. The aliases setup this way will be lost upon a reboot and you will need to recreate those aliases;

2. if you need a more permanent solution, you can edit /etc/network/interfaces file and add alias' definitions there.

For more details on these two methods please visit Ubuntu Linux: Creating ethernet alias for eth0 network device.

If you only needed 2 instances of your program, I would recommende using a virtual machine, but for running five instances you will need 4 virtual machines which is not practical as it will almost halt your machine.

Answer thanks to JoshP in Server Fault:

I just recently did this. See my question. It was kind of a long back and forth, but I did get it set up in the end.

• Set up DNS. The A record will point to your public IP. So, yourdomain.com points to your.pub.ip.add. Add CNAME records for the subdomains. So, sub1.yourdomain.com points to @, and sub2.yourdomain.com points to @, etc. Although the subdomains are all pointing to the same address, the browser will confer to the webserver which subdomain you are trying to reach.

• Set up Apache. You'll want to set up Virtual Hosts for each subdomain (and maybe for primary domain as well). You can define the Virtual Hosts in different places... mine is defined in /etc/apache2/sites-available, and includes the <Location> directive, which is where you'll set up your reverse proxy.

This answer was given to OP in ServerFault.