Protect acess to shared variable network

Hi,
I have a network with applications on several PCs and I used variable of type network-published for communicate between them.
If somebody will do one conection with my network, because there are possibility of conection with my switch, then i can't protect my application.
I want give enable at some variables that everybody can have acess, and another one variables disable acess.
So I want share some variables of my application but not all.
Thank you in advance

Thaks Christian
I found the next link
http://zone.ni.com/devzone/cda/tut/p/id/3322

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Read LabVIEW shared variables ( network variables?) with VB6

Hi, i need to read some LabVIEW shared variables (network variables?) using a VB6 program.
Is it possible?
I think that yes, using Measurement Studio for VB6 but I don't know how and I haven't found information in the Measurement Studio for VB6 help file
Could some one send me a program example or explain me how it is possible to read LabVIEW shared variables fromVB6?

Hello quintella,
To be able to interface with LabVIEW
Shared Variables with Visual Basic 6 you will need to use NI Measurement
Studio, which ships with examples on how to use VB6 with DataSocketing. Apart
from Data Sockets, if you are using Measurement Studio 8.1 or higer, with the
Network Variable Library introducted in NI Measurement Studio 8.1, you can read
and write to shared variables in ANSI C, Visual Basic .NET or Visual C#. (http://zone.ni.com/devzone/cda/tut/p/id/4679)
Here you have two links where you can
find more information about how to use the datasocket option. In addition, there
are several examples included in Measurement Studio with Network Variables and
Datasocket.
http://forums.ni.com/ni/board/message?board.id=230&message.id=2945&requireLogin=False
http://forums.ni.com/ni/board/message?board.id=230&message.id=3324&requireLogin=False
Regards,

Modbus ip shared variable network failure

I am using lab view 8.6 DSC module to communicate to a watlow system which contains five watlow 96 controllers and an EM gateway. I have created shared variables for the process temperatures and setpoints for each of the five controllers using watlow modbus register Numbers with a 400001 offset. I have also created shared variables for Updating,CommFail,UpdateNow,and UpdateRate which where predefined. I have error when starting the VI if the SV has been dragged and dropped into the block diagram. The message is Error -1967353902 (The Modbus I/O server failed to receive any response from the Modbus slave device.) occurred at SV in vi. If I bind a variable in the VI to this same SV the error does not occur but the variable cycles between Good, Network Failure, No known value, and device failure as stated in the variable manager watched variables. The Updating, CommFail and UpdateRate all have a consistent Good in the quality column of the variable manager. UpdateNow has X in value, type, timestamp, and quality columns. CommFail and Updating does cycle between true and false randomly. I have tried a third party software called SpecView 32 demo to see if the commincation with the modbus system is not working and I can create five watlow controlers on my screen and direct them to the ip address along with a unit address and the system works without faults. This leads me to believe the commincation bewteen the SV Engine and the IP address is not correct. HELP Please.
Robert Jensen
UND EERC

If your application can deal with it I would recommend staying clear of the 'Networked Published' option.
When I started my Modbus development on cRIO....I left it enabled, and with ~100 shared variables on a 9074, the CPU was railing, and I saw a buffering behavior on the shared variables (which was not desirable in my application).
In my application I am using the old modbus library (as apposed to the new API) for cRIO to slave comms, the cRIO being the master.
I am also using the IOserver making the cRIO a slave to an external SCADA - and it passes essentially the same data arrays as I use on the modbus library for my local HMI [Not an NI product].....Which is two full Modbus frame writes (@ 120 words each, and about 60 words more for ~300 words outbound from the cRIO).
The IOserver slave was a recent addition and did not add much to the CPU load - although only 16 bytes is high speed, the balance of the total word package is at either 1 second or 3 seconds.
So, in my experince, the 'Networked Published' option adds significant CPU loading (on entery level cRIOs) YMMV.
I am huge fan of the shared variable engine (some at NI were pusing the CVT, and TCE etc...). However most of my shared variables are not the Networked Published variety (excepting local module channels) those have remained networked published for DSM (Distributed System Manager) use.

SLOW PERFORMANCE OF SHARED VARIABLES

Hello,
We have developed application in LabVIEW 8.6.1 for testing mechanical equipments using cRIO 9074 (Real Time controller).
In this application we have used shared variables (Network published) for communications between Real Time controller and Host PC. All shared variables are deployed on Host PC.
Now we want to access the same application(Host PC application) from Tablet PC through wi-fi connectivity.
We have created two seperate .exe to run the application on Host PC and Tablet PC.Shrared variable response for Host PC .exe with RT controller is good,but when we run Tablet PC .exe then response is sluggish(slow).
In this case we create shared variables on Host PC (Network published) and tying to access it from Host PC and Tablet PC.
In our application,
1)Both Host and Tablet PC operate on Windows XP.
2)Programs on Host and Tablet PC are identical.
3)Both PC's are on same subnet.
Please provide appropriate help on this issue.
Thanks in advance....
Sachin

Have you seen this?

Labview 8.2 can't write shared variable

Hi!
I developed LV 8.2 program using shared variable (network published) variant type. After extension of variable the vi charased after writing value in shared variable. If i changed shared variable from network published to single proces type the vi working OK.
Attachments:
problem.jpg ‏23 KB

Hello,
I have created a network published shared variable of type variant, and successfully written to and read from it. Can you also post a snipet of your code which reproduces the problem?
General things to try in case include:
1. undeploy and redeploy the shared variable.
2. repair your LabVIEW installation - this will repair the variable engine, and I know of at least one case where this helped after it was corrupted.
I hope this helps!
Best Regards,
JLS
Best,
JLS
Sixclear

Problems with communication across a network using shared variables

I have two programs(projects) running on two different computers connected with a LAN. I am using LabVIEW 8.0, and the DSC-module. The program on one of the computers have measurements that I want to collect and show on the program running on the other computer on the network. I choose the indicator where I want to show the data, select ''Properties'', ''Data binding'', ''Shared Variable Engine (NI-PSP)'', ''Network Items'' and then browse for a Network...but the problem is that in my ''Network Neighborhood'' There is only one computer...and that is the one I am one...not the computer on my Network that I want to communicate with....
Have anyone any suggestions on how to solve this?
Kind regards Mari

Mari,
Check this link regarding trouble shooting network-published shared variables:
http://digital.ni.com/public.nsf/websearch/6E37AC5435E44F9F862570D2005FEF25?OpenDocument
This might be a firewall issue, so I would check that first.
Frode

Serializing read/write operations of network-published shared variables

Hi all,
I'm developing a distributed application (PC + CompactRIO), and using shared variables (SVs) for inter-device communication. Here's my journey so far:
Intended procedure
PC parses file
PC writes processed file data (custom cluster, large) into the 1st SV
PC writes a "grab data" signal/command (enum) into the 2nd SV
cRIO polls the 2nd SV
cRIO sees the command, then reacts by reading the 1st SV
Steps #2 and #3 were sequenced, using error wires.
Unexpected results
Even after the command is transmitted and the cRIO sees it, the cRIO could not read the data (which I wrote BEFORE the command) -- LabVIEW reported that the buffer was empty.
The operation succeeded when I placed a wait (5 seconds) between steps #2 and #3.
Questions
What am I doing wrong, and how do I achieve my desired outcome?
Is SV I/O asynchronous by design?
Is it possible to use event-driven programming to handle SV access? (i.e. does LabVIEW signal when the new SV value has propagated across the network?)

BillMe wrote:
Why do you have to "notify" the other end that data is available? The subscriber can simply sit in a loop doing a timed read just as if using a queue or notifier IPC. If it doesn't time out, you got new data. If it does time out, do some other processing if needed and then loop back for another timed read.
My sytem architecture is command-driven -- the cRIO listens for instructions from the PC interface (sent as an enum via one SV), and performs tasks (motor control) in response. One of the commands (the one described in this thread) happens to be "download a new motion profile from the PC, by reading the other SV". Given that the cRIO is already polling the command channel, I felt that there's no need to also poll the data channel (especially since the "download" command is issued very infrequenty). Plus, I thought that polling two channels would increase the chances of race conditions or illegal state transitions, particularly if the app is developed over a long term.
I am also new to LabVIEW, so my current programming style will heavily reflect my C++/Qt background while I get a feel for LabVIEW's strengths and weaknesses -- Qt is a heavily event-driven framework (even for networking!), where polling often means you're doing something wrong.
Still, thank you for pointing out that I can use timeouts to determine if new data has arrived -- my subscriber current writes a null command back into the SV when it has consumed the command, but you showed me that I don't have to.

Distributed application: Networked Shared Variables, Named Services (Raw TCP/IP) or Other?

Happy New Year NI forums!
I am working on a project involving mobile interacting robots. In the future it is likely the application's components may need to run on different PCs (Targets). Note: at this point in time all the components are seperate but all running on the localhost machine. Thinking towards the future I want to pick the 'best' architecture to allow all these components (VIs performing various functions) in multiple locations. For example, several VIs on the Robots, VIs on serveral PCs.
I am currently aware of using Server/Client TCP/IP using named services. My mock up works well, but is it time efficient (my time coding) I wonder.. ?
Whereas I am aware of networked shared variables which handle connections and all the parsing for the underlying tcp/ip communication. But will this be difficult the manage? I am unsure if I can associate shared variables with a VI similar to named services. I suppose I could pro grammatically create the variable upon initialization of the server component - and the client could just search the list of avaiaible variables to connect too. Downside this would require DSC module.
As you can see, I am rather unsure. Any advice would be great!
Kind Regards,
James
Kind Regards
James Hillman
Applications Engineer 2008 to 2009 National Instruments UK & Ireland
Loughborough University UK - 2006 to 2011
Remember Kudos those who help!

Hi Jason,
Thanks for your reply. I hope your enjoying NI UK as much as I did.. fun times!
I have seen the link you posted a few times before. But today, I took a better look at it.
My issue is I need several multi-client severs, i.e. many servers which allow multiple clients to connect to them.
Now the STM does have an example of this - STM mutli-client Example - Server.vi (used with the STM mutli-client.vi)
However, when a make copies of these code (to have my second server) - it refuses to run. As in , it just stops itself.
I DID change the port number, on the lister aspect of the server code. But I Am unsure what else I would need to change to get this setup to work?
One thought I had was, the FIFOs all having the same name - this probably isn't a good idea between servers.
Any suggestions would be grateful!
*please could you provide me email support
Kind Regards,
James Hillman
Kind Regards
James Hillman
Applications Engineer 2008 to 2009 National Instruments UK & Ireland
Loughborough University UK - 2006 to 2011
Remember Kudos those who help!

Network shared variables lose binding

Hello,
I am developing an application in LabVIEW that uses network shared variables to transmit data between two PC's on the same subnet. The shared variables work fine when running the VI's in development mode, however, when i build the vi's into an executable I find that they no longer work. Here is what I have found so far:
I deploy the shared variable library on the publisher machine (also happens to be the development machine) through an invoke node in the executable. NI distributed system manager confirms that this does deploy and indeed updates as it should.
For the executable on the subscriber PC I created a second shared variable library (same project) with the same shared variables and bound them to the respective shared variables from the first library by selecting enable aliasing, then bind to PSP URL and browsing to the shared variable I wish to bind it to (e.g. \\hallnet-ellm2\shared variable library\serial Number). The machines listed under browse were listed by name so when I tried this initially and it did not work I manually changed the name of my machine in the URL box to the IP address of the publisher hoping that would fix it in case the subscriber could not resolve the publishers machine alias. So now my bind URL read \\192.168.0.1\shared variable library\serial Number.
As part of the executable on the subscriber I deploy this second shared variable library. NI distributed system manager confirms that this deploys but under quality for an individual variable it has a list of issues (see attached) and the bound variable is not updating. At this point the publisher shared variables are still functioning fine. By clicking on 'edit variable' I can see that the variable on the subscriber is still bound but the PSP URL is now \\localhost\shared variable library\serial number. Changing the PSP URL on the subscriber to \\192.168.0.1\shared variable library\serial number enables the variable to update as expected.However by this time my executable has already picked up the error and does not function.
I think that the issue lies with the bind URL used on the subscriber as for some reason it does not keep the binding configured in the project and instead changes to 'localhost'. Why is this? Should it not stay bound to the address specified in the project?
I have tried changing the IP addresses in the aliases file so that
[My Computer]
My Computer=localhost
becomes
[My Computer]
My Computer=ip of local machine
This did not help.
The shared variable libraries are included in the build spec to go into the support files directory and they are successfully deployed from there on both publisher and subscriber.
I am using LabVIEW 8.6 on Windows XP
Thanks for any help you may be able to offer,
Lee
Attachments:
distributed system manager.JPG ‏74 KB

Hi Lee,
I hope you are well. Thank you for your post. Your application sounds very interesting.
Looking at your issue I was wondering, have you tried lowering your firewalls, as this may be causing the problem.
Also, another option would be to setup a private network. Do you have access to any routers that you could use to link the two machines independent of your IT's infrastructure?
The other thing to try is two other computers entirely. Again, it would be ideal to take them off the network you are on, but it's something to try if my prior suggestion doesn't work. It should work on the original two machines though, and it's likely that different computers won't solve your problems because I suspect the network.
Remember that the client variables must know the location of the variables on the server, so you can't move the server exe around without changing this value.
Make sure to set the network location in the "Bind to Source" option for the client variables.
It is also possible to write a separate piece of code to install on every machine that is responsible for deploying the library and by doing so eliminate the need for programmatically deploying the variables in the original application. However, this won't really help you, because the variables you use in the application have to be the same as the ones deployed in the library, so if you change the library, they'll no longer be linked and they won't receive data. You'd have to create a separate exe for every binding source you wanted to link to, and then have a second, known library for the sake of communication locally on the computer between the ‘deployer’ and the actual application. The main application could then be assigned the responsibility of launching the correct ‘deployer’' if it sees it needs to switch to a different variable binding source. This method is not the most streamlined or effective, but it might work.
Just to let you know, you will need to use the DSC toolkit.
Please find below some knowledge base links that I think you will find helpful in your application.
Using Shared Variables in Executables
How do I Programmatically Change the Data Binding Source for Shared Variables?
I hope this information helps and if you can give these suggestions a go and let me know how you get on, that would be great.
Kind regards,
Prashant M
Applications Engineer
NI UK & Ireland

Not able to access Network Shared Variable when deployed in PC

Initially, when we deploy a Network Published Shared Variable in PC and try to access the same (Read/Write) from RT, we get an error/warning "-1950679023". But when we access the same variable from the PC, it works fine. In the distributed system manager, we can see the variable getting deployed. Also the value changes in Distributed System Manager if we write a value from PC. The attached image "Shared variable Issue.png" will give more understanding of this issue.
The other way round it works fine i.e deploying in RT side and accessing from both RT and PC is working fine.
We also see that the network adapter settings is not loading properly in MAX, if at all we install any software in RT. With no software installed, it loads properly.
The following were the steps that we tried to solve the issue.
1.Flushing the entire NI software and Re- installing again
2.Formatting the RT(PXI).
3.Removing the EtherCAT Card and testing.
4.Checked the network properties of the RT network.
5.Checked the IP/Subnet/Gateway settings.
6.Checked Firewall Settings, If Shared Variable Engine is accessible.
Attachments:
Shared variable Issue.png ‏491 KB

First Root cause needs to be identified before any actions.
I would suggest first check if you can access the shared variable hosted in PC from RT using other ways like using SVE API (Logos and PS protocols, Datasocket etc..)
Check if antivirus or firewall is playing...
Check the same experiment with some other PC if you can.
You can also try creating another Shared Variable in RT and binding the same to the PC and try to access it...
Since you have did all the reinstallations already
Best Regards,
Vijay.

Using network shared variables in two computers connected via a network switch

let me start by saying im a rookie to the programming environment but i have used Labview a couple of times to understand the basics, i have a computer and a laptop (both using vista), both of them with Labview Full development System (Student ed. with Mathscript) installed, so what im tryin to do is to use the built in microphone located in the laptop to aquire sound and then use a Shared Variable to transfere the sound signal from the laptop to the computer, the laptop and the computer are connected to a network via a network switch and ethernet cables, so far i nothing worked, i can manage to create the shared variable in the laptop and use it there but it doesnt appear in the computer, im not sure whats the problem i have even disabled firewalls in both systems, help from anyone wil be appreciated.....

Hi Lukie,
This KB should be of some assistance to you.
Trouble shooting network published shared variables
Also the following link gives some instructions on the use of shared variables.
http://zone.ni.com/reference/en-XX/help/371361B-01/lvhowto/bind_to_source/
I hope this is of some assistance, let me know if you have any more problems.
All the best,
Message Edited by mickeyw on 08-05-2008 12:29 PM
Mike W
Applications Engineer
National Instruments UK&Ireland

Network streams vs shared variables

I send data from a PXI RT System to users on different Windows computers via Shared Variable and Network Stream. The user that receives the data via Network Stream writes the data to a disk file (aka DAQ computer). The users that receive the data via Shared Variable displays it on front panels (aka Observers).
The data consists of a 1D SGL array where elements 0-3 are the timestamp, element 4 is the counter, and elements 5-1000+ are data. The timestamp is GPS time and is displayed on all computers. When I look at the timestamp on the DAQ it is slowly falling behind the current GPS time. After 4 hours it can be up to a minute behind. When I look at the timestamp on the Observers it is always displaying current GPS time. When I look at the code on the PXI System, it is always sending the current GPS time. The counter on the DAQ computer is also behind.
I am using the Read/Write Single Element Stream functions with the default read/write buffer size of 4096. The 'timed out?' output is always FALSE for both functions. No errors are generated. LabVIEW memory usage is constant during the whole time.
On the PXI RT System the Network Stream and Shared Variable are being written to inside a Timed While Loop. The users read the data within a standard While Loop. Everyone is using LabVIEW 2011.
It sounds like a buffer is slowly being filled up somewhere, but where?
Solved!
Go to Solution.

On the PXI RT System:
How often is data sent?
Are you using a “Flush Stream” function after your “Write Single Element to Stream”?
On the “DAQ Computer”:
Are you buffering the reading of the data (i.e. feeding it to a queue)?
You might try using a property node to read “Available Elements for Reading” to see if they are stacking up here.
The buffer size is another option to consider.
steve
Help the forum when you get help. Click the "Solution?" icon on the reply that answers your
question. Give "Kudos" to replies that help.

RT Network Shared Variable and Visa Serial Instr class

Hi,
I'm using Labview 2009 SP1 with the RT module. I've had no problems creating a RT Target application and a Host PC application which are interconnected using Network Shared Variables, until I came to the COM ports fitted to the RT Target (PXI Embedded Controller and 2 x 4 port COM cards).
I can configure and use the COM ports in the RT Target application providing I use constants to define which COM port to use, i.e. VISA OPEN function accepts hardcoded "COM2" , (VISA Serial Instr class).
But I want to pass the COM Port resource name from my host application.
Is there a suitable Network Shared Variable I can create ? or how do I change the string value (COM Port name) of the VISA Serial Instr class variable in the RT Target application ?
thanks,
Gary.

Hi there Gary,
Thanks fot the post. I think I have found something that may be if use to yourself.
http://labviewwiki.org/Functional_global_variable
This is the functional global variable.
Take a look at it and let me know what you think!
Many thanks,
Liam A.
National Instruments
Applications Engineer

Shared variable engine network published source issue

Hello,
I am attempting to use the shared variable engine to share some simple stings over a network between a Windows 7 computer and a Windows XP computer.
I got through the shared variable example just fine and can share variables between VIs on a single computer. When I open the shared variable engine, it shows the client and server variables that are shared on the local computer. I then create a new process, and attempt to define a new variable, and the Shared Variable Property screen comes up. I attempt to "Bind to Source" and click browse, and see the computer name I am attempting to connect to. However, when I click it, it stalls and I cannot expand the computer to find the variable I am trying to bind to. What am I missing?
Thanks, Arron

Arron,
This document may be useful in helping to setup your network shared variables. Take a look at this and see if you have followed all the outlined steps in setting up a network shared variable.
http://zone.ni.com/devzone/cda/tut/p/id/4679
Let me know how this works for you.
-Nick-
Nick C | Staff LabVIEW Platform Product Support Engineer | National Instruments

Binding shared variable in executable across network

I can't seem to get a shared variable to bind from an executable on another computer back to a source variable on the main machine.
I can get the remote variable to change with programmatic access. Is it possible to have shared variables in an executable bind to a PSP URL on another computer? This is labview 2011.
I can see everything with NI Distributed System Manager, and the programmatic access changes the remote variable, so it's not a network issue.
Thanks for any insights. This just doesn't seem to work the way NI's online white papers say it shoud.

What I don't understand is why after binding to a specific URL, the "Shared Variable Deployment" screen of the application builder makes the target "my computer".
I probably could get this to work if I changed the network address of "my computer" in the ini file created in Application Builder?
This seem a strange way for this binding process to work. If the absolute target (for shared variable bound to another variable and referencing "absolute") was retained when the VI goes through the application builder, it would make for sense.
I can't get this to work any way with using bound variables. The only way this works is using programmatic access to shared variables in the built app, and I don't consider this the same thing.
My conclusion is that shared variable binding and appropriate absolute references to deployed variable libraries do not survive passing through the application builder with their absolute references intact.

Protect acess to shared variable network

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