LabView TCP connection

Question

There are some examples in LabView of TCP/IP connection, but I don't really get what the VI is doing. What some functions are doing. Here are the pictures of the examples. Image 1: The Server

Why is the wire splitted into two wires after the typecast function? And I dont really get what these other functions do that are marked.

Image 2: The Client

Answer 1

First, if you don't understand what functions do, learn to open the context help window (ctrl+H) and right click each function to get the specific help for it. This will tell you that the functions read and write to the TCP stream. There should also be some more TCP examples in the example finder, which should have more comments.

As for what's happening, LV represents the TCP byte stream as a string, so whoever wrote the example used the following convention - use type cast to convert to a string, then get the length of that string (an I32, so it's 4 bytes) and type cast that to a string as well and send it before the data.

On the receiving side, the code starts by reading the 4 bytes (because it's an I32) and type casting them back to an I32. This is the length of the rest of the data and it's fed into the second read which then returns the data which is type cast to the original type. This is done because TCP has no terminating character, so this is a convenient method of knowing how much data to read. You don't have to do it like this, but it's an option.