Data lost with TCP connexion (and big data)

[Mathieu33800]

Hello,

I am working on a project on which I have to transfer data from LabVIEW to Python. So Python create the server and launch the VI in two threads, and LabVIEW is the client which send data.

With the current VI, I can send data of a 100*100 table correctly, that is to say each message received in Python contained the entire message, the beginning is the size of the message, and the following the message itself.

But, as soon as I use bigger table (120*120 for example), I don't receive anymore the entire message. It is like this I am at the maximum size of the buffer of the TCP connexion. Is there a maximum size? If yes, do you know it?

Anybody can help me to understand why I am losing data juste changing the size of the table used ?

Thank you in advance

PS: I put the python file but you don't need to look at it. the problem is really in the VI I think.

[billko]

Don't start a new topic on the same subject.  Stick to the old one here.

[Bob_Schor]

Billko,

     Thanks for pointing out that the question was, in fact, answered earlier today in another post.  I'm guessing that possibly there is a language problem, and perhaps the original Poster didn't understand the response that suggested that the Original Poster was trying to send too much data in a single packet.  A quick Web search suggests that the maximum size for a TCP/IP packet is 65535 bytes, but suggests that much smaller packets (less than 10KB) be used.

Bob Schor

[smithd]

There is no link between packet size and the size of the data you pass to the write primitive, at least none I am aware of. The TCP functions package up and transmit the data in whatever sizes make sense (or more likely, whatever sizes the OS takes). 

[Mathieu33800 · Accepted solution]

I see a lot of people visited my page. The solution is on my other post (send after flattening into string and by pieces :

https://forums.ni.com/t5/LabVIEW/Send-big-data-via-network-communication/m-p/3687979#M1037030