What is established when a host receives a request to communicate on a port?

• A. Session
• B. Socket
• C. Connection
• D. Handshake

Answer: (A)

When a host receives a request to communicate on a port, the transport layer sets up a path for data exchange: a connection. In TCP, this starts with a three-way handshake to agree on parameters, after which a dedicated connection is established between the client and server. The operating system then creates a socket to manage that specific connection—the socket is the endpoint used to send and receive the data for that conversation. Sessions are typically an application-layer idea representing ongoing interactions, not the actual transport-layer state that enables data flow. If the service used UDP, there isn’t a formal connection to establish at all, just datagrams arriving on the port.