Hi, as a new Arduino user (but programming veteran) I would like to suggest that the reference help be updated slightly.
E.g. Ethernet - Arduino Reference
The help page does not say whether the call is blocking and also does not say exactly what the call returns if no packet is received.
OK you may say it's obvious, but it's not. The call may have returned 0 (zero) or a negative number as the data type int has a range of -32,768 to 32,767 I also have to put a test Serial.println in to confirm the call wasn't blocking, this would affect the structure of the program. That said it wouldn't be of much use if it was blocking... but for completely and immediate understanding the added information would speed up development time greatly in such instances.
In the example posted perhaps the code could be changed to make it infinitely more readable for new Arduino recruits e.g.
int packetSize = Udp.parsePacket(); // Non blocking
if(packetSize > 0) // Implies that the call Udp.parsePacket() will return 0 on empty packet
{
thanks