//***************************************************************
// From the book "Win32 System Services: The Heart of Windows 98
// and Windows 2000"
// by Marshall Brain
// Published by Prentice Hall
//
// Copyright 1995, by Prentice Hall.
//
// This code demonstrates an extremely simple serial connection.
//***************************************************************

// commtest.cpp

#include <windows.h>
#include <iostream.h>

void ErrorHandler(char *message, DWORD error)
{
	cout << message << endl;
	cout << "Error number = " << error << endl;
	ExitProcess(1);
}

void main()
{
	HANDLE comHandle;
	BOOL success;
	DCB dcb;
	char str[100];
	DWORD numWrite, numRead;
	COMMTIMEOUTS timeouts;
	
	// Open the comm port. Can open COM, LPT,
	// or \\\\.\\TELNET
	comHandle = CreateFile("COM2", 
		GENERIC_READ|GENERIC_WRITE, 
		0, 0, OPEN_EXISTING,
		FILE_ATTRIBUTE_NORMAL, 0);
	if (comHandle == INVALID_HANDLE_VALUE)
		ErrorHandler("In CreateFile",
			GetLastError());

	// Get the current settings of the COMM port 
	success = GetCommState(comHandle, &dcb);
	if (!success) 
		ErrorHandler("In GetCommState",
			GetLastError());

   // Modify the baud rate, etc.
	dcb.BaudRate = 2400;
	dcb.ByteSize = 8;
	dcb.Parity = NOPARITY;
	dcb.StopBits = ONESTOPBIT;

	// Apply the new comm port settings
	success = SetCommState(comHandle, &dcb);
	if (!success) 
		ErrorHandler("In SetCommState",
			GetLastError());

	// Change the ReadIntervalTimeout so that
	// ReadFile will return immediately. See
	// help file
	timeouts.ReadIntervalTimeout = MAXDWORD; 
	timeouts.ReadTotalTimeoutMultiplier = 0;
	timeouts.ReadTotalTimeoutConstant = 0;
	timeouts.WriteTotalTimeoutMultiplier = 0;
	timeouts.WriteTotalTimeoutConstant = 0;
	SetCommTimeouts( comHandle, &timeouts );

	// Set the Data Terminal Ready line
	EscapeCommFunction(comHandle, SETDTR);

	// Send an "at" command to the modem
	// Be sure to use \r rather than \n
	strcpy(str, "at\r");
	success = WriteFile(comHandle, str, strlen(str),
		&numWrite, 0);
	if (!success) 
		ErrorHandler("In WriteFile", GetLastError());

	// Wait 2 seconds and then retrieve from the
	// modem
	Sleep(2000);
	success = ReadFile(comHandle, str,
		100, &numRead, 0);
	if (!success) 
		ErrorHandler("In ReadFile", GetLastError());

	// Print the string received
	cout << numRead << endl;
	str[numRead]='\0';
	cout << str << endl;

	// Clear the DTR line
	EscapeCommFunction(comHandle, CLRDTR);

	CloseHandle(comHandle);  
}