public void Open()
{
fileHandle = SafeNativeMethods.CreateFile(fileName,
SafeNativeMethods.GENERIC_READ | SafeNativeMethods.GENERIC_WRITE,
SafeNativeMethods.FILE_SHARE_READ | SafeNativeMethods.FILE_SHARE_WRITE,
0,
SafeNativeMethods.OPEN_EXISTING,
SafeNativeMethods.FILE_FLAG_OVERLAPPED,
IntPtr.Zero);
int errorCode;
if (fileHandle.IsInvalid)
{
errorCode = Marshal.GetLastWin32Error();
throw new InvalidOperationException($"Error opening COM port. Last Win32 error code is {errorCode}.");
}
ComStat comStat = default;
int errors = 0;
if (SafeNativeMethods.ClearCommError(fileHandle, ref errors, ref comStat) == 0)
{
errorCode = Marshal.GetLastWin32Error();
throw new InvalidOperationException($"ClearCommError returned FALSE. Last Win32 error code is {errorCode}. Error buffer from method contains {errors}.");
}
if (SafeNativeMethods.PurgeComm(fileHandle, SafeNativeMethods.PURGE_RXCLEAR | SafeNativeMethods.PURGE_TXCLEAR) == 0)
{
errorCode = Marshal.GetLastWin32Error();
throw new InvalidOperationException($"PurgeComm returned FALSE. Last Win32 error code is {errorCode}.");
}
DCB dcb = default;
if (SafeNativeMethods.GetCommState(fileHandle, ref dcb) == 0)
{
errorCode = Marshal.GetLastWin32Error();
throw new InvalidOperationException($"GetCommState returned FALSE. Last Win32 error code is {errorCode}.");
}
//Parity in the DCB format is a single character, which happens to correspond to the first character of the enum symbols.
var dcbString = $"baud={baudRate} parity={parity.ToString()[0]} data={dataBits} stop={(int)stopBits}";
if (SafeNativeMethods.BuildCommDCB(dcbString, ref dcb) == 0)
{
errorCode = Marshal.GetLastWin32Error();
throw new InvalidOperationException($"BuildCommDCB returned FALSE. Last Win32 error code is {errorCode}.");
}
if (SafeNativeMethods.SetCommState(fileHandle, ref dcb) == 0)
{
errorCode = Marshal.GetLastWin32Error();
throw new InvalidOperationException($"SetCommState returned FALSE. Last Win32 error code is {errorCode}.");
}
if (SafeNativeMethods.SetupComm(fileHandle, (uint)bufferSize, (uint)bufferSize) == 0)
{
errorCode = Marshal.GetLastWin32Error();
throw new InvalidOperationException($"SetupComm returned FALSE. Last Win32 error code is {errorCode}.");
}
}
internal static extern int ClearCommError(
SafeHandle hFile,
ref int lpErrors,
ref ComStat lpComStat);
