Need small guidance in my networking journey

Hi everyone,
I am completely new in the field of networking. I come here for your guidance. Here is my situation:

There is a custom board(having serial and ethernet ports) and a GUI(developed in VC++). The user will feed the data through the GUI and it has to go the board either through the serial port or through the ethernet port depending on the user's choice.

I am clueless about the Ethernet communication. There are several reference documents available for serial communication, but those on Ethernet are not satisfactory(or say...I am not able to understand much).

Can anyone tell me how to go about this job? I can write a GUI which can transfer data over serial port. But how to transmit it over ethernet? What topics should I read? Do I have to do the transfer by TCP/IP and UDP(I saw that those are used for ethernet)?

Is there a way to do this whole programming using windows API (VC++)?

I know that it is my job to do the task, but can anyone tell me which way to go (or at least in what manner to think)? Thank you.

Beej's Guide to Network Programming

Once you've established the connection (which is a bit more involved than for a serial line), it's pretty much the same (indeed, it would be the same if you were on Unix/Linux).

You write bytes at one end, and bytes appear at the other end.

doesn't winsock solve alot of these problems?