Is the tablet using WiFi to connect to the router? If not, how do you connect both through the same Ethernet port on the tablet?
If you have Ethernet to the Arduino and WiFi to the Router:
Assign a fixed IP address, such as 192.168.17.17, to the Arduino sketch. Last octet must not be '1'.
Assign a fixed IP address, such as 192.168.27.1, to the Ethernet port. First three octets must match the Arduino address. Last octet must be 1.
From the tablet, try to browse to your Arduino: http://192.168.27.17/
This might be sufficient to get it working. Otherwise yoy may need to set the subnet mask to "255.255.255.0"