I have LabVIEW 2015 SP1 loaded on a computer. I need to test to ensure the full path of the Ethernet works right up to the unit under test (UUT). Instead of using the UUT, I have the Tx Hi looped to Rx Hi and Tx Lo to Rx Lo back to itself. I was hoping that I can open its IP address (not localhost) and send data and immediately read it on the read buffer. Nothing. It times out. I have used the standard and CRLF read methods. Can I do this? I prefer not to change the hardware setup. I figure I could wrap Ethernet port 1 to port 2 thorugh the full path.
This is a really weird thing to do. You say "not localhost", but why? "Localhost" is designed for this exact scenario, i.e. hosting a client and a server on the same PC.
Your computer "knows" its IP address, or addresses if it has more than one. If you type in one of those addresses, it will always send it to itself internally and never over an external network connection. So it won't work even if you do something silly like connect one Ethernet port to another on the same PC.
This feels like a classic XY problem to me. Stop, take a step back, and explain your actual problem to us, and then explain why all other possible simulation or testing methods are insufficient and you think that a looped back Ethernet port is the best solution... because it isn't.