problem with trigger

[sunljhhust]

hello,all

1. I create a trigger called "FTP is down on test". It is clone from UNIX_t.

expression: {test:net.tcp.service[ftp].last(0)}=0

the problem is whether the ftp service is started or not, the status and value of this trigger doesn't change.

2 Also,I'm confused by the meaning of the status and value of trigger.

In the manual, I see
{TRIGGER.STATUS}
Trigger state. ON - if trigger is in TRUE state, OFF - if trigger is in FALSE state.
{TRIGGER.VALUE}
Current trigger value:
0 - trigger is in OFF state
1 – trigger is in ON state
2 – trigger UNKNOWN

I'm confused.

Any help?

Thanks