llRequestURL

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Summary

Function: key llRequestURL( );
0.0 Forced Delay
10.0 Energy

Requests one HTTP:// url for use by this object. The http_request event is triggered with the result of the request. HTTP-in uses port 12046.
Returns a handle (a key) used for identifying the result of the request in the http_request event.

Caveats

  • HTTP-in uses port 12046.
  • When a region is (re)started all HTTP server URLs are automatically released and invalidated.
  • The number of available URLs is a limited resource, that is to say, a script can only have so many open URLs. See LSL http_server#Resource Limitations for details.
  • When abandoning a URL, always release it with llReleaseURL, otherwise it will leak.
KBcaution.png Important: Never ever forget to release a URL again which you have requested! URLs are region resources just like prims. If you take them all you can get into big trouble with the sim owner and/or estate managers.

Examples

This script requests a new URL after region restart: 

string url;
key urlRequestId;
key selfCheckRequestId;

reset_script()
{
    llReleaseURL(url);
    llResetScript();
}

request_url()
{
    llReleaseURL(url);
    url = "";

    urlRequestId = llRequestURL();
}

throw_exception(string inputString)
{
    key owner = llGetOwner();
    llInstantMessage(owner, inputString);

    // yeah, bad way to handle exceptions by restarting.
    // However this is just a demo script...

    reset_script();
}

default
{
    on_rez(integer start_param)
    {
        reset_script();
    }

    changed(integer change)
    {
        if (change & (CHANGED_OWNER | CHANGED_INVENTORY))
            reset_script();

        if (change & (CHANGED_REGION | CHANGED_REGION_START | CHANGED_TELEPORT))
            request_url();
    }

    state_entry()
    {
        request_url();
    }

    http_request(key id, string method, string body)
    {
        integer responseStatus = 400;
        string responseBody = "Unsupported method";

        if (method == URL_REQUEST_DENIED)
            throw_exception("The following error occurred while attempting to get a free URL for this device:\n \n" + body);

        else if (method == URL_REQUEST_GRANTED)
        {
            url = body;
            key owner = llGetOwner();
            llLoadURL(owner, "Click to visit my URL!", url);

            // check every 5 mins for dropped URL
            llSetTimerEvent(300.0);
        }
        else if (method == "GET")
        {
            responseStatus = 200;
            responseBody = "Hello world!";
        }
        // else if (method == "POST") ...;
        // else if (method == "PUT") ...;
        // else if (method == "DELETE") { responseStatus = 403; responseBody = "forbidden"; }

        llHTTPResponse(id, responseStatus, responseBody);
    }

    http_response(key id, integer status, list metaData, string body)
    {
        if (id == selfCheckRequestId)
        {
            // If you're not usually doing this,
            // now is a good time to get used to doing it!
            selfCheckRequestId = NULL_KEY;

            if (status != 200)
                request_url();
        }

        else if (id == NULL_KEY)
            throw_exception("Too many HTTP requests too fast!");
    }

    timer()
    {
        selfCheckRequestId = llHTTPRequest(url,
                                [HTTP_METHOD, "GET",
                                    HTTP_VERBOSE_THROTTLE, FALSE,
                                    HTTP_BODY_MAXLENGTH, 16384],
                                "");
    }
}

It's important to keep in mind that if you request another URL, that the old one will not be released, it will remain active. The following script drives home this point.

Try the following code ONLY if you can use all your URLs on your land. Removing the prim/script will release all URLs previous assigned. 

// WARNING:
//
//      This script is only for proof-of-concept (demo purposes).
//      DO NOT use it if you don't have the sim owners and/or
//      estate managers OK to test this script.
//      This script can possibly block HTTP communication from and to the sim.
//      ...bringing down all networked vendors and/or similar machines.
//
//      This script allocates all available URLs.
//      Deleting the script and/or derezzing the object containing the script,
//      will release all previously taken URLs.


default
{
    state_entry()
    {
        llRequestURL();
    }

    http_request(key id, string method, string body)
    {
        if (method == URL_REQUEST_DENIED)
            llSetText("No free URLs!", <1.0, 0.0, 0.0>, 1.0);

        else if (method == URL_REQUEST_GRANTED)
        {
            llSetText( (string)llGetFreeURLs() + " URLs left\n" + body, <1.0, 1.0, 1.0>, 1.0);

            llRequestURL();
        }
        else if (method == "GET")
            llHTTPResponse(id, 200, "Hello there!");
    }
}

This script will, as you can see, use all URLs available on your land because it does not remove the old URLs before requesting a new one.

Just store the old URL in a global variable and release it with llReleaseURL.

Notes

Another comment on resilient programming: getting a global resource, an HTTP listener in this case, should always be considered an operation that can fail for transitory reasons (as well as permanent ones). In this case, LSL folds retryable and permanent errors into the same error status and there's no opportunity for a script writer to distinguish the two cases. But a reasonable way to handle this is sleeping with limited retries before failing hard in the LSL code.
Monty Linden

See Also

Functions

•  llRequestSecureURL
•  llGetFreeURLs
•  llReleaseURL
•  llHTTPResponse
•  llGetHTTPHeader

Articles

•  LSL http server

Deep Notes

History

Signature

function key llRequestURL();
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