Hi @PKOssie,
Sorry, but No a Null Modem Cable is not right!
Both @fintannl & I had been assuming you had your DM500S connected by Ethernet cable to your home network/LAN. An IP address is an Internet Protocol address for use in a computer network. It has no relevance to a null modem connection.
On the other hand, a null modem cable is used for much older RS232 type communication. In the case of a Dreambox, a null modem cable is only used with the DreamUp program to install an image. In most cases, unless the Dreambox has suffered a firmware failure, it will not be necessary to even use a null modem cable for firmware installation. There are other ways.
Anyway, let's proceed. To use an ftp program, DreamboxEdit, the Enigma Web Interface, or to do any of the other things a Dreambox is capable of, you need to connect the Ethernet Socket on the DM500S to a free Ethernet Port on your router. The DM500S is a small Linux computer and the easiest way to 'talk' to it is via its Ethernet connection.
Once you have connected the DM500S to your router, open the network page in the DM500S and note the IP address. Then please re-read what has been posted in this thread carefully. Try what has been suggested to test with a Web Browser, if you can access the Enigma Web Interface. If successful, try ftp-ing the file satellites.xml to DM500S folder /var/etc
Then, reboot, re-scan and what channels are in your channel list?
Good luck & let us know how you get on?
Best wishes, John.