SP_disconnect should be called
when the application is finished with a connection to the
Spread daemon. The application may have other connections
still open to the daemon and may open a new connection after
If any SP_ function returns a CONNECTION_CLOSED or NET_ERRROR_ON_SESSION
error on any call, then the mailbox cannot be used anymore
until it is disconnected with a call to this function and
then reconnected by calling SP_connect(). Any other SP_ calls
will only immediately return the same error value.
The mbox should be for the connection you wish
to disconnect from.