Socket

A socket is a network communication endpoint identified by (protocol, local IP, local port, remote IP, remote port), serving as the interface between the application and transport layers.

Purpose

It gives applications an abstract communication endpoint that hides the underlying protocol details.

Mechanism

The socket API: socket() creates, bind() assigns an address, listen() puts a server in listening mode, accept() takes a connection, connect() dials from the client, send()/recv() transfer data, and close() shuts down. TCP sockets have a state machine; UDP is connectionless.

Use cases

Network servers and clients
Database connections
WebSocket communication
Unix domain sockets (local IPC)

Examples

Input

(TCP, 0.0.0.0:8080, client:1234)

Output

One connected TCP socket

The five-tuple

Common errors

Unclosed sockets exhaust available ports: Use SO_REUSEADDR or close sockets promptly

Related terms

A port is a transport-layer 16-bit address (0-65535) that distinguishes multiple network applications on one host; combined with the IP address it forms a socket.

TCP (Transmission Control Protocol) is a connection-oriented, reliable, ordered transport-layer protocol, establishing connections with a three-way handshake and providing sliding-window flow control and ACK-based acknowledgment.

UDP (User Datagram Protocol) is a connectionless, unreliable, unordered transport-layer protocol with low overhead and minimal delay, suited to real-time and broadcast traffic.

An IP address is the numeric identifier assigned to a network interface—32 bits for IPv4 (four decimal octets) and 128 bits for IPv6 (eight hexadecimal groups)—used for network addressing.

Related tools

Look up common network ports and services. Free, private, 100% client-side.

References