Ethernet

[vrk]

Hi All

I am interested to know much about about the ethernet communication.Please help me how to start with and also forward me if there is any relevant material for this.

Thanks

[smercurio_fc]

http://en.wikipedia.org/wiki/Ethernet

Or, are you asking for something a bit more specific?

[vrk]

Thanks for your reply.

Interested in LabVIEW Ethernet communication.

Thanks

[smercurio_fc]

That's still not very specific. What kind of ethernet communication? What are you trying to do? Transfer a file? Setup a client-server communication scheme? Set up remote control of something? What?

You can start by looking at the examples that ship with LabVIEW. Open the Example Finder (Help -> Find Examples) and do a search for "tcp/ip". You can also try the Knowledge Base, like this article: Basic TCP/IP Communication with LabVIEW.

[vrk]

Thanks

[rsw]

Hi,

TCP communication under LabVIEW is quite straight forward, the main steps are to open/listen, send/recieve and close. As suggested I would recommend looking through the examples, they are fairly well self documented - however if you do have any additional questions regarding the implementation of any of these I'd be glad to help.

All the best,

[mrozack]

What I don't understand in the Simple Data Client example is why TCP read is implemented twice.  It specifies to read 4 bytes, then type casts them, and then reads them again.  These are supposedly the same 4 bytes off the buffer?  How does that work?  Why doesn't the second call read bytes 5-8 from the buffer?

[RavensFan]

The first 4 bytes contain how many more bytes to read.  The type casting is to take the 4 string characters and convert them to a signed 32 bit integer (note the 4 means nothing to the typecast function, only the representation of that constant as I32 matters).  Then take that I32 number and read that many bytes.

Message Edited by Ravens Fan on 04-11-2009 03:38 PM

[mrozack]

Is that the case with all TCP packets?

[RavensFan]

Not necessarily.  I'm not an expert on the TCP/IP protocols, so I can't be sure.  But it would generally be a good idea for the sender to tell the receiver how many bytes is should be expecting to receive.

But if you look at the corresponding example of Simple Data Server, you'll see the size of the data in bytes is prepended to the actual data to be sent.