@SammyG I’d like to make a small correction: it’s UDP 5684 defined as coaps (DTLS-secured CoAP). Devices connecting over TCP will use 5683 defined as coap [1].
At the moment Gen 3 devices also use ephemeral random source ports when establishing connections. The source port range is [49152, 65535] for Argons, Borons and Xenons with Ethernet FeatherWing and [40000, 49000] for Xenons connecting through a gateway.