DataSocket Retention Capabilities

[7J1L1M]

I'm working on an Instant Messenger of some sort, but I need to know the limits of its capabilities. 

If the host computer is off, can another computer still post data to a DataSocket Variable on the host's computer, or is the variable erased?  What happens to the data and variables if both computers are dormant? 

Thanks,

7J1L1M

[Dennis_Knutson]

If the datasocket server is unavailable, you will get an error and if you want to save the data, trap the error and save it locally. I'm not sure what the concern is if the server and client are both turned off. Since you are not publishing any data, there is nothing to lose. If you had been publishing live data, the data is lost as soon as the server is turned off or the VI publishing the data stops sending data.

[7J1L1M]

Hello Dennis,

Thanks for your answer.  The reason I want the data to remain is because I want to also make a sort of email server.  But I want the sender to be able to send the email to the other person using DataSocket even when the computer is off.  In other words, I want to use the DataSocket variables on the other persons computer to serve as a storage bin that other users can put emails into, even when their computer is off.  Is this possible, or would I have to have a seperate computer that is always on and holds the emails until the recipient requests them?

Thanks,

7J1L1M

[Dennis_Knutson]

If you want a server that is always on, then the computer hosting the server has to be always on. If you detect that the server is down, then save it locally as I said and then transmit as soon as the server is detected. Right now my excahnge email server is down at work. If I compose a new email, I can work offline and queue up a bunch of emails for later transmission. You would need to write something similar.

[7J1L1M]

Hello again,

Thank you so much for your help!  One more question. 

What is the difference between FTP and DSTP?  Also, what would happen if I tried to write data to an HTTP website or file link?  Thank you again for your very helpful help! 

7J1L1M

[Dennis_Knutson]

FTP is File Transfer Protocol and is a widely used standard based on TCP/IP. DSTP is NI's proprietary Datasocket Transfer Protocol. I'm not sure about the details on this protocol or whether NI has published much on this. FTP in LabVIEW is supported with the Internet Toolkit.

If you have permission to write to a web site, you would probably be better off using FTP.

[7J1L1M]

So if I say wrote to a webpage that I had permision to do so, would it retain the data I wrote even if the computer that wrote that data was dormant?

7J1L1M

[Dennis_Knutson]

You would be doing a file write and the data would be kept. If you did a file write with datasocket, the data would be saved as well. It's the live data that gets lost. Look at one of the shipping examples for datasocket such as DS Writer. The default target is live data (i.e. dstp://localhost/wave) but there is a text box at the bottom that shows what to specify if you want to write to a file (i.e. dstp://localhost/wave file:examples/comm/dsdata/newwave.dsd).

[7J1L1M]

Thanks for all your help!

7J1L1M