Okay, I have a little experience with networking and Arduino, but not both together. Downplayed a little bit 
My intention: I have a sensor which I would like to read out over TCP/IP or UDP. This is an easy task, there are plenty of examples. But I don't want to set my IP address fix on my notebook, this is inconvenient and annoying. So I can just add a $20 WiFi router and my problem is solved, but I don't like the idea to use an (big) additional device just for DHCP'ing, because I want to carry around this sensor. I known, a WiFi shield could be an option too.
So I would like to plug in my network cable, get an IP address and read out my sensor data with my windows-/mac-application (IP address of my Arduino DHCP server is fix).
Unfortunately, I have deleted all changed projects. DHCPLite looks very good but I had to rewrite the RedFly stuff and use 'default' Ethernet/UDP and failed. (Ethernet.h, EthernetUDP.h)
I take a look again and post the code here with my problems.