turn on and off a listen

Hello,
Had a friend as if it was possible to turn on and off a listen. I said no. but then he showed me:
ListenRemove: Removes listen event callback
ListenControl: Makes listen event callback active or inactive
i have never used these so i don't know anything about them.
is it possible to turn off listen?

Yes your friend told you correctly.
You can find more information at http://www.lslwiki.org/index.php/LlListen

You set up a means of identifying the listener e.g. a global called handle:

integer handle;

Then, when calling your listen you assign it to the handler e.g.:

handle=llListen(1001, "", llGetOwner(), "";

and when you want to turn it off you call its handle:

llListenRemove(handle);

I rarely use llListenControl, but it's the same sort of structure.

I usually do a llSetTimerEvent before I set a listener. Then inside the timer() event I put in a ListenRemove, llSetTimerEvent(0), and llSay(0,"Response not recieved". Your user now has a certain amount of time to say the command before the listen dies.

The downside is they must click on the object, or get a menu to invoke the listener. They can't just walk up to the object and give a command.

I use lockable windows on my house (saves cutting out door shapes) with the option to switch listening on and off for when I want to add authorized users, selected from a dialog.

Using an integer for chandle and cchan, and m is the received message from the dialog:

if(m=="Listen on"){
    chandle=llListen(cchan,"",llGetOwner(),"");
}else if(m=="Listen off"){
    llListenRemove(chandle);
}

There's not much info available on llListenControl, so I don't know whether it removes the listen from the servers list of listeners, or simply stops the triggering of the event. With llListenRemove you know it's been removed from the list so should be easy on the server if you aren't switching it on and off too many times.

thank you all very much for your replies. they were all helpful.