How does a TCP connection differ from an application-level session?

TCP provides an ordered, reliable byte stream between endpoints while the connection is viable; it does not define user identity, messages, or login state. An application session represents higher-level state and may span several transport connections. Conversely, one persistent connection can carry multiple requests. Applications must define message framing, authentication, deadlines, and how to recover when a connection fails after a request may already have been processed. A successful write to a local socket buffer does not prove the remote application completed the operation.