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LabVIEW Actor Framework – Linked Network Actor

Member

Following on from the LabVIEW Actor Framework Basics post, I wanted to continue the project showing how to use a Linked Network Actor. The Linked Network Actor (LNA) library uses network streams to communicate between Actors across a network connection. You can download the library and read all about the details over on the community page.

Either start at the beginning of the previous post, or just download the project here.

Once you have the project open, start by creating a new class, Remote Actor, and setting its inheritance to Actor.

LabVIEW Actor Framework Remote Actor Inheritance

Next you need to add the Linked Network Actor library to your project. If you used VIPM to install the library, you can find the lvlib in the following location. C:\Program Files (x86)\National Instruments\LabVIEW 2013\vi.lib\NI\Actors\Linked Network Actor

LabVIEW Actor Framework Linked Network Actor.lvlib

For your newly created Remote Actor, follow the steps in the previous post for overriding 'Pre Launch Actor.vi', 'Actor Core.vi' and 'Stop Core.vi'. You will also need to create a launcher VI to start the Remote Actor. All these steps have been covered before and you will be left with four VIs that look as follows.

LabVIEW Actor Framework Pre Launch Init

LabVIEW Actor Framework Actor Core

LabVIEW Actor Framework Stop Core

LabVIEW Actor Framework Remote Launcher

You will now have a normal Actor that can be run from the launcher and will stop cleanly when the front panel of the Actor Core is closed.

Adding the Linked Network Actor - Remote Actor

Create a global VI which is used to define the Remote Actor identity, Local Actor identity and the IP Address of the Remote Actor. I have used a global VI in this example to keep these settings in one place, but in a proper application, these values should be saved in some sort of config file and then added in using the constructors.

Actor Framework LNA names

Now we need to create the Launch LNA VI and the Kill LNA VI. The Launch LNA VI will be run from the Remote Actor Core and the Kill LNA VI will be run from the Remote Stop Core.

In the Launch LNA VI, you need to launch an instance of 'Linked Network Actor.lvclass'. However, before the Actor is launched, a few properties need set. Using the global VI from above, set the name to be RemoteActor, set a buffer size and a timeout. Once these properties are set, the Actor can be launched using the Remote Actor as the enquerer. Make sure to set the front panel to FALSE and wire the Remote LNA Enqueuer into the private data of Remote Actor. This enqueuer will be needed later when we want to send messages.

LabVIEW Actor Framework Remote Actor Launch LNA

Next we need to create the Remote Kill LNA VI which wraps the Send Normal Stop VI and is called from the Remote Stop Core. This will stop the Remote LNA when the Remote Actor is stopped.

LabVIEW Actor Framework Remote Kill LNA

Local Actor

Once we have the Remote LNA running, we need a local LNA that is going to connect to it. Once this connection is made, messages can be sent between Actors across a network.

Again we need to create a Launch LNA and Kill LNA VI which will be launched by the Parent (local) Actor Core and stopped by the Parent (local) Stop Core respectively. Both VIs are similar to the Remote version, except for a few additions to the Launch LNA VI.

In the Parent Launch LNA VI, we need to specify connection URL which consists of the Remote Name and Remote IP Address. Once this URL has been constructed, we can run the 'Send Connect.vi' which is part of the LNA library.

LabVIEW Actor Framework Parent Launch LNA

The Parent Kill LNA VI also uses the Send Normal Stop VI and is run from the Parent Stop Core.

Sending a Message

Once you have the Remote LNA and Parent LNA set up, all you need to do is create a method to run and build a message using the Actor Framework Message Maker tool. Then when you want to send a message, unbundle the LNA enqueuer and wire the message into the 'Send Transmit Network Message.vi'. This will execute the remote method referenced in the message Do.vi.

LabVIEW Actor Framework Send LNA Message

If you need to send data as part of the message, you will be able to add the data to the message using property nodes.

Messages can now be sent across a network with ease.

As usual the working project can be found here and if you have any comments or advice, please send me an email or alternatively leave a comment on Google+. When running the program, make sure you start Remote Actor first, and then Launch the Parent Actor. It must be done this way as the Parent connects to the Remote.

Greg

Comments
Member

The parent actor terminates with an error -314004 when the remote actor isn't launched. Is there a method to check the connection before firing an error?

Member

Hi Ludwig,

I have had a quick look and from what I am seeing the error is being generated in Linked Network Actor.lvclass:Connect.vi, as is expected.

I am not sure why the error is not being propogated up to Parent Actor.lvclass:Launch Local LNA.vi. If it was then you can retry connecting there.

There might be a method in the new version of the LNA library or Actor Framework library but I am not sure. I'll have a look a little later when I get more time to see if there is a way of accessing the error without it just shutting down the actor.

Cheers,

Greg

Member

I use the newest LNA and Actor Framework libraries. In my eyes the problem is, that the Linked Network Actor.lvclass:Connect.vi is only a message sender. There is no direct feedback if the connection can't be established. The error occurs later in the execution - probably when the timeout run out.

Member

That is what I was thinking. I just did a quick test by changing the timeout set before launching the local LNA in Launch Local LNA.vi. This timeout determines when the error is thrown.

This might be a question for the Actor Framework community.