It seems to me that the Exosite library writeRead() function for the Arduino is weak with rxdata buffer overflow issues. I am no software developer whiz so haven’t worked out the best way to robustly fix the problem yet. I think the while loop that transfers characters from the client to the rxdata buffer needs another AND condition to stop the loop when stringPos reaches the end of the rxdata buffer. I have observed situations simultaneously with Wireshark and the Atmel Studio IDE debugger where the rxdata buffer overflows with normal chaos ensuing because other variables get overwritten. With the usual TCP packet loss and retransmissions, sometimes Exosite responses to the Arduino device get retransmitted such that more than one respone arrives at the Arduino device immediately one after the other and flood the rxdata buffer. It quite happliy overwites stuff including critical things like the Arduino millis() counter until the sketch crashes completely.