This function initializes the communications parameters for a specified communications device.
BOOL SetupComm( HANDLE hFile, DWORD dwInQueue, DWORD dwOutQueue );
Always returns FALSE because the FIFO queue size cannot be changed. To obtain extended error information, call GetLastError.
After a process uses the CreateFile function to open a handle to a communications device, it can call SetupComm to set the communications parameters for the device. If it does not set them, the device uses the default parameters when the first call to another communications function occurs.
The dwInQueue and dwOutQueue parameters specify the recommended sizes for the internal buffers used by the driver for the specified device. For example, YMODEM protocol packets are slightly larger than 1024 bytes. Therefore, a recommended buffer size might be 1200 bytes for YMODEM communications.
The device driver receives the recommended buffer sizes, but is free to use any I/O buffering scheme as long as it provides reasonable performance and data is not lost due to overrun (except under extreme circumstances).
For example, the function can succeed even though the driver does not allocate a buffer, as long as some other portion of the system provides equivalent functionality.