If you've worked with the Arduino Ethernet Shield, you've probably noticed a limitation: while you can connect to an IP address, you can only reach the default virtual host on that server. This becomes a problem when working with shared hosting or VPS servers that host multiple websites on a single IP address.
The Problem
Modern web servers commonly use virtual hosting to serve multiple websites from a single IP address. When you make a basic HTTP request to an IP, the server returns the default site—not necessarily the one you want. On commercial shared hosting, you typically can't make your site the default host.