Windows Networking APIs

Winsock API

The Windows Sockets API (Winsock) is a Microsoft-specific implementation of the Berkeley sockets API. It provides a set of functions and data structures for network communication.

• socket(): Creates a socket.
• bind(): Associates a local address with a socket.
• connect(): Establishes a connection to a remote host.
• listen(): Puts a socket into a listening state.
• accept(): Accepts an incoming connection request.
• send() / recv(): Sends and receives data.
• closesocket(): Closes a socket.

For more details, see the Winsock Programming Guide.

Example: Simple TCP Client

#include <winsock2.h>
#include <ws2tcpip.h>
#include <stdio.h>

#pragma comment(lib, "Ws2_32.lib")

int main() {
    WSADATA wsaData;
    SOCKET ConnectSocket = INVALID_SOCKET;
    struct sockaddr_in clientService;
    int port = 27015;

    if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0) {
        printf("WSAStartup failed.\n");
        return 1;
    }

    ConnectSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (ConnectSocket == INVALID_SOCKET) {
        printf("Error at socket(): %ld\n", WSAGetLastError());
        WSACleanup();
        return 1;
    }

    clientService.sin_family = AF_INET;
    clientService.sin_addr.s_addr = inet_addr("127.0.0.1");
    clientService.sin_port = htons(port);

    if (connect(ConnectSocket, (SOCKADDR*)&clientService, sizeof(clientService)) == SOCKET_ERROR) {
        printf("connect failed with error: %d\n", WSAGetLastError());
        closesocket(ConnectSocket);
        WSACleanup();
        return 1;
    }

    printf("Connected to server!\n");

    // Send and receive data...

    closesocket(ConnectSocket);
    WSACleanup();
    return 0;
}
            

DNS Resolution APIs

• getaddrinfo(): A modern, thread-safe function for resolving hostnames and service names.
• gethostbyname(): An older function for resolving hostnames.

See Name Resolution Documentation for more information.

WinINet API

The WinINet API provides high-level access to the Hypertext Transfer Protocol (HTTP) and the File Transfer Protocol (FTP). It simplifies common internet tasks.

• InternetOpen()
• InternetOpenUrl()
• HttpSendRequest()

Also consider the Windows HTTP Services (WinHTTP) API for server-side applications or system services.