This function transmits a specified character ahead of any pending data in the output buffer of the specified communications device.
Nonzero indicates success. Zero indicates failure. To obtain extended error information, call the GetLastError function.
The TransmitCommChar function is useful for sending an interrupt character (such as a CTRL+C) to a host system.
If the device is not transmitting, TransmitCommChar cannot be called repeatedly.
After TransmitCommChar places a character in the output buffer, the character must be transmitted before the function can be called again.
If the previous character has not been sent, TransmitCommChar returns an error.