GenericMessageUDP - Revision history

Acryline at 14:09, 5 March 2015

2015-03-05T14:09:46Z

Justincc at 18:09, 26 June 2014

2014-06-26T18:09:38Z

Justincc at 18:01, 26 June 2014

2014-06-26T18:01:20Z

Justincc at 17:43, 26 June 2014

2014-06-26T17:43:04Z

Justincc: Created page with "=Introduction= Within the LLUDP protocol, there is a message type called GenericMessage. This has the following structure (taken from a viewer's app_settings/message_templat..."

2014-06-26T17:36:37Z

Created page with "=Introduction= Within the LLUDP protocol, there is a message type called GenericMessage. This has the following structure (taken from a viewer's app_settings/message_templat..."

New page

=Introduction=

Within the LLUDP protocol, there is a message type called GenericMessage. This has the following structure (taken from a viewer's app_settings/message_template.msg file).

GenericMessage Low 261 NotTrusted Zerocoded
{
AgentData Single
{ AgentID LLUUID }
{ SessionID LLUUID }
{ TransactionID LLUUID }
}
{
MethodData Single
{ Method Variable 1 }
{ Invoice LLUUID }
}
{
ParamList Variable
{ Parameter Variable 1 }
}

[http://wiki.secondlife.com/wiki/GenericMessage Linden Lab uses this message for some miscellaneous functionality]. However, because we can switch messages on the Method parameter, we can also use GenericMessage as a carrier of arbitrary UDP data between the client/viewer and the simulator, as GenericMessages can flow both ways.

= Example =
Typically, we would create an OpenSimulator [[IRegionModule|region module]] to subscribe to the GenericMessages with certain Method names.

← Older revision		Revision as of 14:09, 5 March 2015
Line 1:		Line 1:
		+	{{Languages\|GenericMessageUDP}}
	=Introduction=		=Introduction=

← Older revision		Revision as of 18:09, 26 June 2014
Line 97:		Line 97:
	# logpacket 100 packets.log		# logpacket 100 packets.log

−	shortly before triggering the sendgeneric command, you should see the reply in packets.log.	+	shortly before triggering the sendgeneric command, you should see the reply from the region module in the packets.log file.
		+
		+	= Further steps =
		+	Of course, once a region module receives a generic UDP message, it is not limited to just replying with a GenericMessage to the client. Any behaviour can be triggered, such as performing some processing and then sending GenericMessages back to every client/viewer connected to the region.
		+
		+	= Caveats =
		+
		+	Although GenericMessages work in this test scenario, I (justincc) am not currently aware of anybody actually using the mechanism for sending and receiving arbitary UDP from a libopenmetaverse client/modified viewer to an OpenSimulator region module. So whilst it should work, further use might reveal problems of which we are not yet aware.
		+
		+	There shouldn't be a size limit problem, though one has to be carefully not to exceed the UDP size limit. I believe that messages under 4K bytes should be fine.
		+
		+	Also, one has to know the exact format of messages flying back and forth - they are not self-describing. This is expected in a UDP context where the idea is very quickly receive and process time-critical data. However, if you need to move data back and forth that is not so time-critical and would benefit from greater reliability, you might want to consider implementing a new HTTP [[capabilities\|capability]] in your region module for communication back and forth with the client. The issue here is that to send data directly to the client (rather than as a reply to some other request), one might need to implement a custom event queue message, which might not yet be possible in OpenSimulator.

@@ Line 23: / Line 23: @@
 = Example =
 Typically, we would create an OpenSimulator [[IRegionModule|region module]] to subscribe to the GenericMessages with certain Method names.  There is an example GenericMessagingModule at https://github.com/justincc/GenericMessagingModule which does exactly this.  We will extract the important parts here.
-First thing to do is to have the region module subscribe to incoming GenericMessages from viewers with a particular method name.  The module looks for a method named "Test", but in a real application you would want to pick a name which is very unlikely to be used by Linden Lab in the future or any other OpenSimulator extension.  Here's the code snippet.
+The first thing to do is to have the region module subscribe to incoming GenericMessages from viewers with a particular method name.  Here's the code snippet.
 <source lang="csharp">
@@ Line 47: / Line 49: @@
+}
 </source>

← Older revision		Revision as of 17:43, 26 June 2014
Line 23:		Line 23:

	= Example =		= Example =
−	Typically, we would create an OpenSimulator [[IRegionModule\|region module]] to subscribe to the GenericMessages with certain Method names.	+	Typically, we would create an OpenSimulator [[IRegionModule\|region module]] to subscribe to the GenericMessages with certain Method names. There is an example GenericMessagingModule at https://github.com/justincc/GenericMessagingModule which does exactly this. We will extract the important parts here.
		+
		+	First thing to do is to have the region module subscribe to incoming GenericMessages from viewers with a particular method name. The module looks for a method named "Test", but in a real application you would want to pick a name which is very unlikely to be used by Linden Lab in the future or any other OpenSimulator extension. Here's the code snippet.
		+
		+	<source lang="csharp">
		+	public void AddRegion(Scene scene)
		+	{
		+	scene.EventManager.OnNewClient += HandleNewClient;
		+	}
		+
		+	private void HandleNewClient(IClientAPI client)
		+	{
		+	client.AddGenericPacketHandler("test", HandleGenericMessage);
		+	}
		+
		+	private void HandleGenericMessage(object sender, string method, List<string> args)
		+	{
		+	IClientAPI client = (IClientAPI)sender;
		+
		+	m_log.DebugFormat(
		+	"[GENERIC MESSAGE]: Received message with method {0}, args {1} from {2} in {3}",
		+	method, string.Join("\|", args.ToArray()), client.Name, client.Scene.Name);
		+	}
		+	</source>