linux select编程

int select(int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, struct timeval *timeout);

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/select.h>

#define MAX_CLIENTS 10
#define BUFFER_SIZE 1024

int main() {
    int server_fd, new_socket;
    struct sockaddr_in address;
    int addrlen = sizeof(address);
    char buffer[BUFFER_SIZE] = {0};
    fd_set readfds;
    int max_sd, activity, i, valread, sd;

    // 创建socket
    if ((server_fd = socket(AF_INET, SOCK_STREAM, 0)) == 0) {
        perror("socket failed");
        exit(EXIT_FAILURE);
    }

    // 绑定socket
    address.sin_family = AF_INET;
    address.sin_addr.s_addr = INADDR_ANY;
    address.sin_port = htons(8080);
    if (bind(server_fd, (struct sockaddr *)&address, sizeof(address)) < 0) {
        perror("bind failed");
        exit(EXIT_FAILURE);
    }

    // 监听
    if (listen(server_fd, 3) < 0) {
        perror("listen");
        exit(EXIT_FAILURE);
    }

    int client_sockets[MAX_CLIENTS] = {0};

    while (1) {
        // 清空文件描述符集合
        FD_ZERO(&readfds);

        // 添加服务器socket到集合
        FD_SET(server_fd, &readfds);
        max_sd = server_fd;

        // 添加客户端sockets到集合
        for (i = 0; i < MAX_CLIENTS; i++) {
            sd = client_sockets[i];

            // 如果socket不为0，则添加到集合
            if (sd > 0) {
                FD_SET(sd, &readfds);
            }

            // 高的socket描述符
            if (sd > max_sd) {
                max_sd = sd;
            }
        }

        // 等待事件发生
        activity = select(max_sd + 1, &readfds, NULL, NULL, NULL);

        if ((activity < 0) && (errno != EINTR)) {
            perror("select error");
        }

        // 如果服务器socket有活动，则接受新的连接
        if (FD_ISSET(server_fd, &readfds)) {
            if ((new_socket = accept(server_fd, (struct sockaddr *)&address, (socklen_t*)&addrlen)) < 0) {
                perror("accept");
                exit(EXIT_FAILURE);
            }

            // 添加新的socket到数组
            for (i = 0; i < MAX_CLIENTS; i++) {
                if (client_sockets[i] == 0) {
                    client_sockets[i] = new_socket;
                    break;
                }
            }
        }

        // 检查所有客户端sockets
        for (i = 0; i < MAX_CLIENTS; i++) {
            sd = client_sockets[i];

            if (FD_ISSET(sd, &readfds)) {
                // 读取数据
                if ((valread = read(sd, buffer, BUFFER_SIZE)) == 0) {
                    // 客户端断开连接
                    getpeername(sd, (struct sockaddr*)&address, (socklen_t*)&addrlen);
                    printf("Host disconnected, ip %s, port %d\n", inet_ntoa(address.sin_addr), ntohs(address.sin_port));
                    close(sd);
                    client_sockets[i] = 0;
                } else {
                    // 发送回数据
                    send(sd, buffer, valread, 0);
                }
            }
        }
    }

    return 0;
}