Help writing a simple Ymodem Send

Hey there, I'm fairly new to programming but have been tasked with writing a Ymodem send program to send some data that I parsed out to hardware. So far I have parsed data into a char array, and then opened up a serial port. I just don't know where to begin in writing a Ymodem send program (the receiving end was written by someone else). Here is my code for opening the serial port, now I am stuck in implementing the actual Ymodem protocol. I have searched for code online but most of it makes use of extra libraries that I don't have. I am currently writing this in Visual C++ . Any help would be greatly appreciated, Thanks!

Code for Serial Port:
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Code:

#include "stdafx.h"
#include "windows.h"
#include "string.h"
#include "stdio.h"

HANDLE hComPort;
BOOL SetCommDefaults(HANDLE hSerial);

int main()
{
	hComPort = CreateFile("\\\\.\\COM24", GENERIC_READ | GENERIC_WRITE, 0, 0, OPEN_EXISTING, 0, 0);
	if (hComPort == INVALID_HANDLE_VALUE){
			return FALSE;
			SetCommDefaults(hComPort);
			printf("E012_Failed to open port");
	}else{

	SetCommDefaults(hComPort);
	
	DWORD dwBytesRead =0;
	DWORD dwBytesWritten =1;

	char buf[50];

		sprintf(buf,"I am connected to hyperterminal\n");

		WriteFile(hComPort, buf, strlen(buf), &dwBytesWritten,NULL);
	}

		CloseHandle(hComPort);

		return 0;
}


BOOL SetCommDefaults(HANDLE hComPort)
{
	DCB dcb;
	dcb.BaudRate = 115200;
	dcb.ByteSize = 8;
	dcb.Parity = 0;
	dcb.StopBits = ONESTOPBIT;
	dcb.fDtrControl = DTR_CONTROL_DISABLE;
	dcb.fDtrControl = RTS_CONTROL_DISABLE;
	
	if(!SetCommState(hComPort, &dcb))
		return FALSE;
	return TRUE;
}

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