Eternal loop in EthernetClass::socketSendUDP

When sending UDP using the W5xxx, sometimes the Arduino freezes permanently. Probably if another packet is arriving at the same time one is to be sent.

I created this ticket in the old repo in 2018, and it is still a problem as verified by @bleckers and @gioblu.
Full details here:

https://github.com/arduino-libraries/Ethernet/issues/78