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By drjdpowell
An extensive library for passing messages between parallel processes. Generalizes the communication method, allowing the message sender to use the method provided by the receiver. Supported communication methods include wrappings of simple queues, user events, and notifiers, as well a more complex channels such as a TCP server and client. In addition, one can configure simple forwarding addresses (“Observers"), which can send messages to multiple destinations, optionally with modifications such as adding a prefix to the message label, relabelling, or substituting a different message.
Communication patterns supported include request-reply (asynchronous or synchronous), where the reply is sent to a "reply address" attached to the request, and register-notify, where one process sends a registration message to another in order to subscribe to a series of updates. Also supports scatter-gather, the gathering of replies from multiple senders into an array of messages.
An option framework for dynamically-launched VI "actors" is also provided, including example templates, which can be accessed via the Tools menu (from an open Project, select Tools>>Messenger Library>>Create Actor from Template..). An "Actor Manager" debug tool is also installed under the Tools menu. Please note that this package has nothing directly to do with the NI Actor Framework (other than both packages are influenced by the Actor Model).
***Introductory Videos are on a YouTube channel.***
***A great summary of many Messenger Library sources, provided by Bob W Edwards***
Original conversation on this work is here.
Now hosted on the LabVIEW Tools Network (but note that the latest version will often be on LAVA)
***NOTE: latest versions require VIPM 2017 or later to install.***
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By drjdpowell
I've started to make some instructional videos on YouTube for my Messenger Library. I was inspired by Delacor's nice videos on their new DQMH framework and also by Steve Watts' CSLUG channel. Any feedback appreciated.
James
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By drjdpowell
I’m hoping to add some sample projects to my “Messenging” package, and I thought it would be easy and instructive to rework one of NI’s templates, “Continuous Measurement and Logging”, as it is already somewhat actor-like with three communicating modules. Attached is a (back-saved for 2011) copy of the NI project, with my version included (run “Main.vi” for the original, “Main.lvclass:Actor.vi” for my version).
I kept the basic functionality the same, but couldn’t resist changing some of the UI (in the old code, “Main” controls the UI; in the new code, published state messages from the Acquisition and Logging Actors set the UI).
Continuous Measurment and Logging with Messenging.zip
Any comments appreciated. Is this example less clear than the NI original? Why? How could I improve it?
In particular, is code like this (the most complicated interaction, I think) understandable without heavy documentation? It’s a “Start Logger, then Start Acquisition, then Unset the Busy Cursor” three-actor chain message:
I’m thinking of making a “Send Chain Message” subVI (that accepts arrays of addresses and message labels) to replace the above code.
— James
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By torekp
At http://zone.ni.com/d...a/epd/p/id/4394, NI provides some example code for using Windows Messaging in Labview 2009. But the example generates and intercepts the messages in the same single toplevel VI. Is it possible to converse between two VIs using Windows Messaging? Would I need (or be able) to create a new DLL in order to do that?
Toplevel:
Create Windows Message Queue:
From the Readme file:
**How it works**
A DLL included does all of the dirty work. The VIs in the library are primarily
wrappers around the DLL with the exception of Wait for Windows Message.vi.
When creating the first Windows message queue, the DLL installs a windows Get Message Hook and a CallMsgProc Hook on the LabVIEW process. This allows the DLL to inspect all messages heading for LabVIEW before LabVIEW processes them. The hook function determines whether each individual message is a message in which the queue is interested. If it is, it adds the message to the queue, and sets an occurrence. The Wait on Windows Message.vi is waiting on the same occurrence, and thus it continues its execution, retrieving the message from the queue. A number of utility functions are also provided for working with the queue.
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Any advice appreciated, even if it's "abandon all hope". (I'm a very weak C programmer.) I'm attaching the CPP code for the DLL, as a text file.
Windows Messages for LabVIEW.txt
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