An error message will pop up if you have the Automatic Error Handling option enabled in the VI Properties window and you haven't wired an Error Out terminal. You can get rid of it either by unchecking the option or wiring the Error Out terminal on the TCP primitive.
In general, error handling is very important and you should always wire error clusters into something which will handle errors for you. For example, you can decide to stop the program if one error occurs and to restart it if another occurs (for example 56 which is a TCP timeout error).
To learn more about LabVIEW, I suggest you try searching this site and google for LabVIEW tutorials.
Here and
here are a couple you can start with and
here are some tutorial videos. You can also contact your local NI office and join one of their courses.
In addition, I suggest you read
the LabVIEW style guide and the LabVIEW user manual (Help>>Search the LabVIEW Bookshelf).
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