What is a socket and a socket pair?

A socket is an IP address plus a port number; a socket pair is the source and destination sockets together, which uniquely identifies a single conversation.

Sockets and Socket Pairs:

Socket: The combination of an IP address and a port number.

Socket Pair: The combination of source and destination sockets that uniquely identifies a conversation.

Format:

Source Socket:      192.168.1.5:49152
Destination Socket: 93.184.216.34:80
Socket Pair:        192.168.1.5:49152 ↔ 93.184.216.34:80

Why Sockets Matter:

• Enable multiple processes on a client to distinguish themselves
• Allow multiple connections to a server process
• Uniquely identify each conversation

Example - Multiple Browser Tabs:

Tab 1: 192.168.1.5:49152 ↔ server:80
Tab 2: 192.168.1.5:49153 ↔ server:80
Tab 3: 192.168.1.5:49154 ↔ server:80

Each tab uses a different source port to maintain separate sessions.

Go deeper:

• Network socket — defines the socket as an IP+port endpoint and the 4-tuple socket pair.
• Port (computer networking) — the port half of the socket and how it scopes a service.