I see frequent errors where the network connection to my Arduino Uno WiFi drops when I am requesting a web page. I wrote a simple REST server, and some of the pages will load as expected, but others will fail after loading half of the the text, and I notice that the network connection drops in the middle of these events. Why is the network connection dropping like this?
I saw this error when I was running low on RAM. The Arduino Uno WiFi appears to drop the network connection in low memory situations. One fix that made a significant difference for my program was to wrap all of the string literals in the F() macro. This moves the strings from ram to flash storage, and in my case quickly freed 500 bytes of SRAM (25% of the available RAM on this board). For example, replace:
client.println("HTTP/1.1 200 OK");
client.println(F("HTTP/1.1 200 OK"));
Some other memory optimization may also be necessary. Another possible cause of these symptoms would be low voltage, possibly from trying to draw too much power from the board to power external devices, but in my case there were no external connections, and I confirmed it was a low-memory issue.