The following functions are used to unbind from the directory,
    close the connection, and dispose of the session handle.

            int ldap_unbind( LDAP *ld );
            int ldap_unbind_s( LDAP *ld );

    Parameter is as follows:

    ld    The session handle.

    The ldap_unbind() and ldap_unbind_s()  functions both work
    synchronously, unbinding from the directory, closing the
    connection, and freeing up the ld structure before returning.
    There is no server response to an unbind operation. The ldap_
    unbind() function returns LDAP_SUCCESS (or another LDAP error
    code if the request cannot be sent to the LDAP server). After a
    call to ldap_unbind() or ldap_unbind_s(),  the session handle ld
    is invalid and it is illegal to make any further LDAP API calls
    using ld.