Difference between revisions of "LlListen"

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(note limitation of negative channel number)
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**llListen(0,"",NULL_KEY,"") is extremely laggy as it listens to all chat from everyone in chat range and should be avoided at all cost.
**llListen(0,"",NULL_KEY,"") is extremely laggy as it listens to all chat from everyone in chat range and should be avoided at all cost.
*Negative channel numbers can only be used for inter object communication (and are preferable in that case).
*Negative channel numbers can only be used for inter object communication (and are preferable in that case).
**This may just be an artificial limitation placed on the client and not the underlying protocol.
|examples=
|examples=
Trivial example to listen to any chat from the object owner and respond once. To reduce lag and avoid spamming surrounding users, it is vastly preferable to listen on channels other than 0 and to trigger the listen event by chatting on an alternative channel such as '/5 hello'.
Trivial example to listen to any chat from the object owner and respond once. To reduce lag and avoid spamming surrounding users, it is vastly preferable to listen on channels other than 0 and to trigger the listen event by chatting on an alternative channel such as '/5 hello'.

Revision as of 21:03, 8 August 2007

Summary

Function: integer llListen( integer channel, string name, key id, string msg );
0.0 Forced Delay
10.0 Energy

Sets a callback for msg on channel from name and id.
Returns an integer that can be used to deactivate or remove the listen.

• integer channel any valid integer, positive or negative.
• string name
• key id
• string msg

If msg, name or id are blank they are not used to filter incoming messages.
If id is an invalid key or a null key, it is considered blank.

Channel Constant Description
DEBUG_CHANNEL 0x7FFFFFFF Chat channel reserved for script debugging and error messages, broadcasts to all nearby users.
PUBLIC_CHANNEL 0x0 Chat channel that broadcasts to all nearby users. This channel is sometimes referred to as: open chat, local chat and public chat.

Caveats

  • On state change or script reset all listens are released.
    • A state change can be used as a shortcut to releasing listens.
  • Only 64 listens can simultaneously be open in any single script.
    • If this number is exceeded an error is shouted.
  • Avoid channel 0 and set name or id where possible to avoid lag. (Lag)
    • llListen(0,"",NULL_KEY,"") is extremely laggy as it listens to all chat from everyone in chat range and should be avoided at all cost.
  • Negative channel numbers can only be used for inter object communication (and are preferable in that case).
    • This may just be an artificial limitation placed on the client and not the underlying protocol.

Examples

Trivial example to listen to any chat from the object owner and respond once. To reduce lag and avoid spamming surrounding users, it is vastly preferable to listen on channels other than 0 and to trigger the listen event by chatting on an alternative channel such as '/5 hello'.

// says beep to owner the first time owner says something in main chat;
integer listen_handle;

default
{
    state_entry()
    {   //Registers the listen to the owner of the object at the moment of the call. This does not automatically update when the owner changes.
        // Change 0 to another positive number to listen for '/5 hello' style of chat.
        listen_handle = llListen(0, "", llGetOwner(), "");
    }
    listen( integer channel, string name, key id, string message )
    {
        llOwnerSay("beep");
        // Stop listening until script is reset
        llListenRemove(listen_handle);
    }
    on_rez(integer param)
    {   //Triggered when the object is rezed, like after the object had been sold from a vendor
        llResetScript();//By resetting the script on rez it forces the listen to re-register.
    }
    changed(integer mask)
    {   //Triggered when the object containing this script changes owner.
        if(mask & CHANGED_OWNER)
        {
            llResetScript();
        }
    }
}

See Also

Events

•  listen

Functions

•  llListenRemove Removes a listen
•  llListenControl Enables/Disables a listen
•  llWhisper Sends chat limited to 10 meters
•  llSay Sends chat limited to 20 meters
•  llShout Sends chat limited to 100 meters

Deep Notes

Signature

function integer llListen( integer channel, string name, key id, string msg );