C语言select方式实现socket实例

最新推荐文章于 2025-06-18 14:11:47 发布

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#select #socket #网络编程 #C语言

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本文介绍了一个使用C语言实现的简易非阻塞TCP服务器，该服务器通过select机制监听连接并处理客户端请求。代码展示了如何创建socket、设置非阻塞模式、绑定地址、监听连接以及接受客户端连接。

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server.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <errno.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/epoll.h>
#include <time.h>
#include <sys/select.h>

#define MAX_FD_NUM 3

void setnonblock(int fd) {
    int flag = fcntl(fd, F_GETFL, 0);
    if (flag == -1) {
        printf("get fcntl flag %s\n", strerror(errno));
        return;
    }
    int ret = fcntl(fd, F_SETFL, flag | O_NONBLOCK);
    if (ret == -1) {
        printf("set fcntl non-blocking %s\n", strerror(errno));
        return;
    }
}

int socket_create(int port) {
    int fd = socket(AF_INET, SOCK_STREAM, 0);
    if (fd == -1) {
        printf("socket create %s\n", strerror(errno));
        return -1;
    }
    setnonblock(fd);
    struct sockaddr_in addr;
    memset(&addr, 0, sizeof(addr));
    addr.sin_family = AF_INET;
    addr.sin_port = htons(port);
    addr.sin_addr.s_addr = htonl(INADDR_ANY);
    if (bind(fd, (struct sockaddr *)&addr, sizeof(addr)) == -1) {
        printf("socket bind %s\n", strerror(errno));
        return -1;
    }
    if (listen(fd, 20) == -1) {
        printf("socket listen %s\n", strerror(errno));
        return -1;
    }
    return fd;
}

void socket_accept(int fd) {
    int max_fd = fd, i = 0;
    fd_set readfds;
    int clients[MAX_FD_NUM];
    for (; i<MAX_FD_NUM; ++i) {
        clients[i] = -1;
    }
    int client_fd, len;
    while (1) {
        FD_ZERO(&readfds);
        FD_SET(fd, &readfds);
        for (i=0; i<MAX_FD_NUM; ++i) {
            if (clients[i] != -1) {
                FD_SET(clients[i], &readfds);
            }
            if (clients[i] > max_fd) {
                max_fd = clients[i];
            }
        }
        int ret = select(max_fd+1, &readfds, NULL, NULL, NULL);
        if (ret == -1) {
            printf("select %s\n", strerror(errno));
            return;
        }
        if (FD_ISSET(fd, &readfds)) {
            struct sockaddr_in addr;
            memset(&addr, 0, sizeof(addr));
            len = sizeof(addr);
            client_fd = accept(fd, (struct sockaddr *)&addr, &len);
            if (client_fd == -1) {
                printf("socket accept %s\n", strerror(errno));
                break;
            }
            for(i=0; i<MAX_FD_NUM; ++i) {
                if (clients[i] == -1) {
                    clients[i] = client_fd;
                    break;
                }
            }
            continue;
        }
        for(i=0; i<MAX_FD_NUM; ++i) {
            if(FD_ISSET(clients[i], &readfds)) {
                char buf[64];
                memset(buf, 0, sizeof(buf));
                recv(clients[i], buf, sizeof(buf), 0);
                printf("%s", buf);
                close(clients[i]);
                clients[i] = -1;
            }
        }
    }
    close(fd);
}

void server() {
    int fd = socket_create(8080);
    if (fd == -1) {
        printf("socket create fd failed\n");
        return;
    }
    socket_accept(fd);
}

int main(int argc, char *argv[]) {
    server();
    return 0;
}