After testing the code on these hardware prototypes, I designed my customized hardware. The schematic is provided below.
To be mentioned:
1. I used switching regulator LM2596 as linear regulator was getting heated up a lot.
2. The interrupt pin of W5100 is connected to interrupt pin of Arduino.
3. Added buzzer for when there is any problem, buzzer will be made ON.
4. Used ADM2484 as RS485 transreceiver IC.
The schematic file can be downloaded from "Files" section.