accept Function (Winsock)

Synopsis

SOCKET accept(
    SOCKET s,
    struct sockaddr *addr,
    int *addrlen
);

Parameters

s – A descriptor identifying the socket that will accept connections.
addr – A pointer to a buffer that receives the address of the connecting entity. Can be NULL.
addrlen – On input, specifies the size of the buffer pointed to by addr. On output, receives the actual size of the address.

Return Value

If the function succeeds, the return value is a new socket descriptor for the accepted connection. If it fails, the return value is SOCKET_ERROR. Call WSAGetLastError for extended error information.

Remarks

Typical usage

#include <winsock2.h>
#pragma comment(lib, "Ws2_32.lib")

int main() {
    WSADATA wsa;
    SOCKET listenSock, clientSock;
    struct sockaddr_in server, client;
    int clientLen = sizeof(client);

    WSAStartup(MAKEWORD(2,2), &wsa);

    listenSock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    server.sin_family = AF_INET;
    server.sin_addr.s_addr = INADDR_ANY;
    server.sin_port = htons(5555);
    bind(listenSock, (SOCKADDR*)&server, sizeof(server));
    listen(listenSock, 5);

    clientSock = accept(listenSock, (SOCKADDR*)&client, &clientLen);
    if (clientSock == SOCKET_ERROR) {
        printf("accept failed: %d\\n", WSAGetLastError());
        return 1;
    }

    // Communicate with client using recv/send ...

    closesocket(clientSock);
    closesocket(listenSock);
    WSACleanup();
    return 0;
}

This snippet demonstrates a basic TCP server that creates a listening socket, binds it to a local port, and accepts an incoming connection.

Examples

Simple Echo Server

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

#define PORT 8080
#define BUF_SIZE 512

int main() {
    WSADATA wsa;
    SOCKET listener, client;
    struct sockaddr_in server, clientAddr;
    int clientAddrLen = sizeof(clientAddr);
    char buf[BUF_SIZE];
    int bytesRecv;

    WSAStartup(MAKEWORD(2,2), &wsa);

    listener = socket(AF_INET, SOCK_STREAM, 0);
    server.sin_family = AF_INET;
    server.sin_addr.s_addr = INADDR_ANY;
    server.sin_port = htons(PORT);
    bind(listener, (SOCKADDR*)&server, sizeof(server));
    listen(listener, 5);

    printf("Server listening on port %d...\\n", PORT);
    client = accept(listener, (SOCKADDR*)&clientAddr, &clientAddrLen);
    if (client == SOCKET_ERROR) {
        printf("accept error: %d\\n", WSAGetLastError());
        return 1;
    }

    while ((bytesRecv = recv(client, buf, BUF_SIZE, 0)) > 0) {
        send(client, buf, bytesRecv, 0);
    }

    closesocket(client);
    closesocket(listener);
    WSACleanup();
    return 0;
}

Winsock API Reference