I use TCP vi to send string to arduinos (arduino uno+ arduino wifi shield, and they have arduino code preloaded inside ) wirelessly through the router. Sometimes they can communicate well, the arduino receive the string send by the TCP vi. But sometimes, there will be an error 66 come out of TCP Write vi, so, labview loop will stop. Arduino will say "connection failed". And I have config the VI sever allow the arduino to access.
Another thing I want to mention is, when I highlight the execution, the error will come out more frequently.