Winsock API Reference: Introduction

The Windows Sockets API (Winsock) is a Microsoft Windows-specific application programming interface (API) for programs that need to communicate over TCP/IP networks. It is based on the Berkeley sockets API used in UNIX systems.

Winsock provides a standardized way for applications to interact with the underlying network protocols, allowing for both client-server and peer-to-peer communication. It supports a wide range of networking tasks, from simple data transfer to complex network services.

Key Concepts

Sockets

At the core of Winsock is the concept of a socket. A socket is an endpoint for communication. It's an abstract representation of a network connection, defined by an IP address and a port number. Winsock provides functions to create, bind, connect, send, receive, and close sockets.

Protocols

Winsock supports various network protocols, most commonly Transmission Control Protocol (TCP) and User Datagram Protocol (UDP). TCP provides a reliable, ordered, and error-checked stream of data, while UDP offers a faster, connectionless datagram service.

TCP (Transmission Control Protocol): Connection-oriented, reliable delivery.
UDP (User Datagram Protocol): Connectionless, unreliable but faster delivery.

Address Families

Winsock supports different address families, which define the structure of network addresses. The most common is AF_INET for IPv4 addresses. AF_INET6 is used for IPv6 addresses.

Getting Started

To use Winsock in your application, you typically need to:

Initialize the Winsock library using the WSAStartup function.
Create a socket using the socket function, specifying the address family, socket type, and protocol.
If you are creating a server, bind the socket to a specific port and IP address using bind, and then listen for incoming connections with listen.
If you are creating a client, connect to a server using connect.
Send and receive data using functions like send, recv, sendto, and recvfrom.
Close the socket when communication is finished.
Clean up Winsock resources using WSACleanup.

Note: It is crucial to call WSAStartup before any other Winsock functions and WSACleanup when your application is finished with Winsock.