IOCTL_SERIAL_SET_RTS control code
The IOCTL_SERIAL_SET_RTS request sets RTS (request to send).
If a handshake flow control of the device is configured to automatically use RTS, a client cannot clear or set RTS.
A client can use an IOCTL_SERIAL_CLR_RTS request to clear RTS.
The Information member is set to zero.
The Status member is set to one of the Generic Status Values for Serial Device Control Requests. A status of STATUS_INVALID_PARAMETER indicates that the handshake flow control of the device is set to automatically use RTS.