PROGRAM tdfzone (OUTPUT);

VAR

    tdf        : UNSIGNED;
    tdf_handle : [VOLATILE] UNSIGNED;

[ASYNCHRONOUS,UNBOUND]
PROCEDURE ast_system_event;
BEGIN

    LIB$SPAWN ('@SYS$STARTUP:TCPIP$NTP_SHUTDOWN.COM');
    LIB$SPAWN ('@SYS$STARTUP:TCPIP$NTP_STARTUP.COM');

    $SET_SYSTEM_EVENT ( SYSEVT$C_TDF_CHANGE,
                        ast_system_event,
                        ,
                        ,
                        SYSEVT$M_REPEAT_NOTIFY,
                        tdf_handle
                        );

    $WAKE;

END;

BEGIN

    WHILE TRUE DO
    BEGIN

        $SET_SYSTEM_EVENT (SYSEVT$C_TDF_CHANGE,
                           ast_system_event,
                           ,
                           ,
                           SYSEVT$M_REPEAT_NOTIFY,
                           tdf_handle
                          );

        $HIBER;

    END;

END.