What is a port number?

The choice that defines a port number as a logical connection for specifying server programs is accurate because port numbers serve as specific endpoints in network communications. Each port number corresponds to a specific service or application running on a server, allowing multiple services to operate simultaneously over a single IP address.

For example, when you access a website, your browser typically communicates over port 80 for HTTP or port 443 for HTTPS, directing the traffic to the web server's specific application handling those protocols. This logical separation is crucial for network efficiency and functionality, enabling computers to manage multiple network connections without interference.

In contrast, other concepts like physical identifiers for network cables, measures of bandwidth, or unique addresses (like IP addresses) pertain to different aspects of networking that do not involve the notion of ports directly, emphasizing why the definition focused on logical connections is the most appropriate response.