Deletes the sending background buffer
COM_SFLUSH(<nComPort>) --> lDeleted
<nComPort> Designates the port (1 to N) for which the sending
buffer is deleted.
If the selected sending buffer is successfully deleted, the function
returns a .T.
COM_SFLUSH() eliminates all the characters in a sending buffer. This
can be useful when the send routine has been futilely waiting for an XON
character (bad software handshake).
” A COM_SFLUSH() to a closed port does not work.
” It is not necessary to test for characters in the sending
buffer to carry out a COM_SFLUSH().