UDP Honesty Boundary - UDP Ports Find the Socket

The toy datagram checks bytes and endpoint numbers; it does not model network behavior.

highlighted = computed this step

What this toy datagram proves

This book proves exact field decoding and checksum verification for one tiny UDP datagram. It does not model an operating-system socket API.

\text{datagrams}=1

The source port 40000, destination port 53, length 10, and checksum 0x779f are all recomputed from pinned bytes.

40000\to53

NOTE: toy UDP datagram only; not socket APIs, NAT, firewall behavior, retransmission, ordering, congestion, or production network capture.

\text{toy datagram only}=1

UDP ports find a socket-side endpoint name in this toy, while the checksum verifies exact bytes only.

\text{valid fold}=0xffff