correct the 'Diagram 4.24' with 'Diagram 4.9'
correct the 'expected cost 300 RMB' with 'expected cost 200 RMB'
correct the 'service layer' with 'business logic layer'
uniform the ips in Chapter 5.2.3 with 192.168.1.177 only
refine Chapter 5.2.3
uniform all the Arduino Ethernet IP address with 192.168.1.1