configuration for remote control with Labview by WLAN

[Fran 41]

I would like to remotely control a PC from a laptop (both running Labview), to be for instance able to remotely launch VIs or stop them, and receive data from the remote computer. They are linked by a wireless LAN.
What configuring must I do? And what is the procedure to control the remote pc? Must I use vi-servers? If I do, how?
Thank a lot !

[mikeporter]

Yes, the way to do it is with VI server. There are several examples that ship with LV that show how to do this. The main key is that calling VIs that exist on your own machine and calling ones on a remote computer are the same except that for remote VIs you have to open a reference to the copy of LV running on the other computer, whereas with local calls you don't.

If you can give more details, I can give more specific advice.

Mike...

[FraserD]

Mike,

Thanks for the reply.

We have tried with the example VI Server and VI Client in the examples that ships with LV. Inputting the IP addresses and then the computer names into the "machine list" box on these VIs didn't work. We then tried to set up the IP address details within {Remote Systems > Create New > Devices not on local subnet} MAX. As we are trying to create the wireless link between only two machines we did this in MAX for both of them.

When we browse our wireless network status within the proprietary software that comes with the IEEE802.11b devices (one of which is USB and one is PCMCIA) there is a network connection.

So other than the preliminaries with respect to making sure LV recognises our connection, the problem i
s how to set up the REFNUM, to be able to remotely operate VI's. Is this process set up within the LV program?

We have searched the ni.com for support docs, but we haven't really found anything which tells us how to set up the remote link.

We've attached the VI Server example.

We appreciate your advice in helping get our application running.

Fran/FraserD

[mikeporter]

Attached is a very simple client. If you set the VI type reference appropriately (which basically defines it's connector pane), this code should be able to call a VI on another machine and return it's data. A couple points:

1. LV has to be already running on the other machine.
2. LV on the other machine has to have remote access turned-on. (The three VI Server screens under "Tools>>Options...")
3. You have to know the remote machine's IP address, or if you have a DNS, it's name.
4. You have to know what port the remote copy of LV is listening to. It's one of the parameters you'll be setting in Step 2.

Mike...

[Fran 41]

Mike,

Thank you very much for your help.
I tried the VI you sent, it indeed seems to be what we need.
I have followed your instructions, and it runs OK until it arrives to the 'Open VI reference'.
Out of that come error 7 (file not found), even though the path given for the VI I want to run on the remote machine is correct, and that that VI is configured as exported (tools>options) on the remote machine.
To set the VI type reference, I right-clicked on it in the pannel: Select VI server class>Strictly typed VIs>Copied from cached class 0 (it's the only one in the list). Is that wrong?
Must the VI I want to remotely call suit specific requirements? (I have attached a simple VI I would like to run). Or what configuration must be do
ne on the remote machine?

Thanks again !

Fran

[mikeporter]

The error you're getting is that the file isn't found. To tell the truth, whenever I've tried this the VI I'm wanting to control was already in memory. Something to try is have the VI open on the remote machine and try calling it. For this test replace the path with a string constant containing just the name of the VI you're wanting to call. My expectation is that this will work.

If that works, you know that the type is setup correctly. Speaking of which in the menu you mentioned there is a "Browse..." option. Select that and in the resulting dialog box select a copy of the VI you're trying to control that exists on your local machine--or at least one that has an identical connector pane.

Finally, make sure you're conn
ecting to the computer you think you are. For example, the function to get the application reference should fail with an error if LV isn't running on the remote machine.

One more thing, what operating systems are the two machine's running? What exactly does the path look like that you are sending to Open VI Reference?

Mike...

[Fran 41]

Mike,

I get the same error whether the VI on the remote machine is in memory or not. I had also used the Browse>... option, but then the VI won't run (broken arrow).
Anyway, it seems as though there is a network problem: when I run the VI without Labview runing on the remote computer (and even when the remote machine is switched off!) I have exactly the same error number (7). No error comes out of the application reference.
The only machine connected to the laptop is the one I want to 'see', with a WLAN connection. When I check the local network it finds the connection, with the right machine.
What could the problem be with this wireless connection? I have checked the IP adress and the port number I have set in the 'tes
t VI'. When I set any other IP adress I get error 56 out of the application reference.
Could there be a compatibility problem between the LAN pcmcia card (Bluetake 802.11b PC card) and the LAN adapter ('W-Buddie' WN210, IEEE802.11b too)?
The laptop is runing on windows XP pro, and the remote machine on windows 2000. Could this cause problems?

Thank you very much for your help !

Fran

[mikeporter]

The operating system shouldn't be a problem. When you select a new VI for the "type specifier VI Refnum" you sometimes have to right click on the Call by Reference node and select "Adapt to Reference Input".

Mike...

[Fran 41]

Mike,

I have been trying to make this wireless connection work, in vain until now...
I therefore have another few questions you could perhaps answer:
I have tried imposing an IP adress to each computer, the remote-server-vi-test still doesn't run (error 56).
- is it normal both machines send packets, but neither receive any?
- could the problem be that 'enable internet sharing for this connection' (local area connection>properties>sharing) is not clicked?
If it is, what port numbers must I input or how can I find them (the 'remote server port number' and the 'incoming response port'(TCP))?
- the two computers are not on the same domain. I have created a domain on the laptop and then tried to add the
remote machine to it, but this won't work (impossible to see the other machine in the 'network places' of any of the two computers). Could this prevent the vi from working? And is it normal?
Or could you see anything else potentially wrong?

I would be extremely grateful if you could answer these questions. Thank you very much again,

Fran