Week 8: Ports, Transport, and Service Exposure

An IP address identifies a network-layer destination. A service still needs a transport endpoint and a listening process. This week connects TCP and UDP behavior to sockets, ports, service binding, and defensive exposure decisions.

You will read supplied handshake and socket evidence, distinguish “listening” from “reachable,” and reason about a fictional service that was bound more broadly than intended.

This week

1. Ports Belong to Transport Endpoints — connect process, protocol, address, and port without treating port numbers as applications.
2. TCP Keeps Connection State; UDP Does Not Promise It — interpret handshake and datagram evidence carefully.
3. Listening Is Not the Same as Reachable — compare bind address, route/path, and policy to narrow service exposure.

Evidence artifact

Create a Service Exposure Record with socket baseline, transport evidence, intended client set, changed binding, control decision, retest, and limitation.