Hi. KS Lam
You have to different set each W7100A.
For example, left W7100A set TCP server and right W7100A set TCP client.
You don’t directly connection. You must connect with HUB.
(W7100A) — (LAN cable) — (HUB) — (LANCable) — (W7100A)
However If it doesn’t working, you should test each W7100A. such as loopback test.
If each W7100A loopback test is work well, I think it is wrong hub or not good connection.