Arduino Uno Ethernet Problems with Shared Servers / DNS

This tutorial is written for the WizNet W5100 Module. In case you or your hoster shares one server IP with multiple users you will have a problem when following the Arduino.cc tutorials. The problem is you will not even notice that you use an outdated HTTP 1.0 (HTTP 1.1 Spec), because most servers will reply with something like: Please use your domainname instead of this IP.

To fix it simply switch to HTTP 1.1 and add your Host to validate that request. Here is an example for the motioncoding servers:

BAD:
client.println("GET /some/path/on/your/server HTTP/1.0");

FIX:
client.println("GET /some/path/on/your/server HTTP/1.1");
client.println("Host: motioncoding.de");