Is serDclose(); enough to close a RS232 connection?

Hello.
I’ve got a program that is almost done, but I’ve got one problem.
When I send something over port D I get a ACK back (from the device on port D (rs232 communication))
When I wait to long. I have to reconnect te com port. (close port en open port again.)
When I do this with a com port tool kit. It is no problem.
So I want to know if my code is wright:
serDclose();
serDopen(_232BAUD);
ClearTransmitBuffers();
ClearReceiveBuffers();
etc …
and then further with my code to send again data to port B. (rs232)
Can someone tell me if this is the wrigt procedure to close and open a RS232 connection?
thanx