Let’s start by asking is writing the code for RS-232c and Ethernet coding language the same? Let’s us an example: Denon AVR
(COMMAND and PARAMETER list:

COMMAND PARAMETER function example
PW ON POWER ON/STANDBY change PWON
STANDBY PWSTANDBY
? Return PW Status PW?
)

COMMAND and PARAMETER list:

COMMAND – PW, the PARAMETER – ON, and the FUNCTION – POWER ON/STANDBY CHANGE, the EXAMPLE – PWON

COMMAND – PW, the PARAMETER – STANDBY, and the FUNCTION – this is blank, the EXAMPLE – PWSTANDBY

COMMAND – PW, the PARAMETER – ?, and the FUNCTION – Return PW Status, the EXAMPLE – PW?


Connector specification:
Ⅰ. RS-232C
Connector type: DB-9pin female type, slave straight connection (DCE type)
( 1pin : GND , 2pin : TxD , 3pin : RxD , 5pin : Common(GND) ,4,6,7,8,9pin : NC )

Communication format:
Synchronous system : Tone step synchronization
Communication system : A half duplex
Communication speed : 9600bps
Character length : 8 bits
Parity control : None
Start bit : 1 bit
Stop bit : 1 bit
Communication procedure : Non procedural
Communication data length : 135 bytes (maximum)

Ⅱ. Ethernet
Ethernet Cross cable PC to/from AVR/AVC
Ethernet Straight cable HUB PC to/from AVR/AVC
Connector type ： RJ-45(10BASE-T/100BASE-TX)

Communication format ：

Communication system : A half duplex
Communication speed : 10Mbps/100Mbps
Communication port : TCP port 23 (telnet)
Communication data length : 135bytes (maximum)