What defines a socket in networking?

A socket in networking is indeed defined as a unique pair of IP and port numbers. This pairing allows specific processes to communicate over a network. The IP address identifies a device on the network, while the port number identifies a specific service or application running on that device. When combined, they create a socket that enables sending and receiving data between applications across the network.

This concept is fundamental in enabling multiple services to run on a single IP address by differentiating them through their port numbers. Each socket is essentially a communication endpoint that allows for a specific, directed communication channel, ensuring that data sent over the network reaches the correct destination and service.

Other choices do not accurately define a socket. A single port alone does not represent the complete context of communication, as it lacks the necessary IP address which is crucial for identifying the specific machine. A digital signal is more about the physical layer of communication rather than the networking concepts of sockets. Similarly, protocols are important for establishing and managing connections, but they are separate from the definition and function of a socket itself.