I'm writing a class to integrate a POS card reader device to our software. In order for it to work I must know what IP it's using. We were given some sample code by the service provider and the way they do this is they open a website (http://www.ebizchargeemv.com/getip.php?mac={MAC address of device}) and it would return the IP address of the device. The device I'm using is a POSLynx220 Mini. It has an ethernet port that connects to the internet to communicate with the service provider. I send TCP data to it and the device then controls a PIN pad that prompts a client to swipe his card. It's probably a mini computer that communicates with the service provider and uses the PIN pad as its input device. Just being curious but how did they implement this? Are they implementing it using ARP? I'm planning on not using their website to determine the IP of the device. I've seen some code that uses ARP but using executing ARP in one of the PC didn't detect the POS device.