博客地址：https://www.hz-bin.cn/epoll-server-client

服务端

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <sys/epoll.h>

#define SERVER_PORT         (7778)
#define EPOLL_MAX_NUM       (2048)
#define BUFFER_MAX_LEN      (4096)
char buffer[BUFFER_MAX_LEN];

void str_toupper(char *str) {
    int i;
    for (i = 0; i < strlen(str); i++) {
        str[i] = toupper(str[i]);
    }
}

int main(int argc, char **argv) {
    int listen_fd = 0;
    int client_fd = 0;
    struct sockaddr_in server_addr;
    struct sockaddr_in client_addr;
    socklen_t client_len;
    int epfd = 0;
    struct epoll_event event, *my_events;
    // socket
    listen_fd = socket(AF_INET, SOCK_STREAM, 0);
    // bind
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    server_addr.sin_port = htons(SERVER_PORT);
    bind(listen_fd, (struct sockaddr*) &server_addr, sizeof(server_addr));
    // listen
    listen(listen_fd, 10);
    // epoll create
    epfd = epoll_create(EPOLL_MAX_NUM);
    if (epfd < 0) {
        perror("epoll create");
        goto END;
    }
    // listen_fd -> epoll
    event.events = EPOLLIN;
    event.data.fd = listen_fd;
    if (epoll_ctl(epfd, EPOLL_CTL_ADD, listen_fd, &event) < 0) {
        perror("epoll ctl add listen_fd ");
        goto END;
    }
    my_events = (epoll_event*) malloc(sizeof(struct epoll_event) * EPOLL_MAX_NUM);

    printf("start success\n");
    while (1) {
        // epoll wait
        int active_fds_cnt = epoll_wait(epfd, my_events, EPOLL_MAX_NUM, -1);
        int i = 0;
        for (i = 0; i < active_fds_cnt; i++) {
            // if fd == listen_fd
            if (my_events[i].data.fd == listen_fd) {
                //accept
                client_fd = accept(listen_fd, (struct sockaddr*) &client_addr, &client_len);
                if (client_fd < 0) {
                    perror("accept");
                    continue;
                }
                char ip[20];
                printf("new connection[%s:%d]\n", inet_ntop(AF_INET, &client_addr.sin_addr, ip, sizeof(ip)),
                        ntohs(client_addr.sin_port));
                event.events = EPOLLIN | EPOLLET;
                event.data.fd = client_fd;
                epoll_ctl(epfd, EPOLL_CTL_ADD, client_fd, &event);
            } else if (my_events[i].events & EPOLLIN) {
                printf("EPOLLIN\n");
                client_fd = my_events[i].data.fd;
                // do read
                buffer[0] = '\0';
                int n = read(client_fd, buffer, BUFFER_MAX_LEN);
                if (n < 0) {
                    perror("read");
                    continue;
                } else if (n == 0) {
                    epoll_ctl(epfd, EPOLL_CTL_DEL, client_fd, &event);
                    close(client_fd);
                } else {
                    printf("[read]: %s\n", buffer);
                    buffer[n] = '\0';
#if 1
                    str_toupper(buffer);
                    write(client_fd, buffer, strlen(buffer));
                    printf("[write]: %s\n", buffer);
                    memset(buffer, 0, BUFFER_MAX_LEN);
#endif
                    /*
                     event.events = EPOLLOUT;
                     event.data.fd = client_fd;
                     epoll_ctl(epfd, EPOLL_CTL_MOD, client_fd, &event);
                     */
                }
            } else if (my_events[i].events & EPOLLOUT) {
                printf("EPOLLOUT\n");
                /*
                 client_fd = my_events[i].data.fd;
                 str_toupper(buffer);
                 write(client_fd, buffer, strlen(buffer));
                 printf("[write]: %s\n", buffer);
                 memset(buffer, 0, BUFFER_MAX_LEN);
                 event.events = EPOLLIN;
                 event.data.fd = client_fd;
                 epoll_ctl(epfd, EPOLL_CTL_MOD, client_fd, &event);
                 */
            }
        }
    }
    END: close(epfd);
    close(listen_fd);
    return 0;
}

客户端

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <fcntl.h>

#define MAX_LINE (1024)
#define SERVER_PORT (7778)

void setnoblocking(int fd) {
    int opts = 0;
    opts = fcntl(fd, F_GETFL);
    opts = opts | O_NONBLOCK;
    fcntl(fd, F_SETFL);
}

int main(int argc, char **argv) {
    int sockfd;
    char recvline[MAX_LINE + 1] = { 0 };
    struct sockaddr_in server_addr;
    if (argc != 2) {
        fprintf(stderr, "usage ./client <SERVER_IP>\n");
        exit(0);
    }
    // 创建socket
    if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
        fprintf(stderr, "socket error");
        exit(0);
    }
    // server addr 赋值
    bzero(&server_addr, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(SERVER_PORT);
    if (inet_pton(AF_INET, argv[1], &server_addr.sin_addr) <= 0) {
        fprintf(stderr, "inet_pton error for %s", argv[1]);
        exit(0);
    }
    // 链接服务端
    if (connect(sockfd, (struct sockaddr*) &server_addr, sizeof(server_addr)) < 0) {
        perror("connect");
        fprintf(stderr, "connect error\n");
        exit(0);
    }
    setnoblocking(sockfd);
    char input[100];
    int n = 0;
    int count = 0;
    // 不断的从标准输入字符串
    while (fgets(input, 100, stdin) != NULL) {
        printf("[send] %s\n", input);
        n = 0;
        // 把输入的字符串发送 到 服务器中去
        n = send(sockfd, input, strlen(input), 0);
        if (n < 0) {
            perror("send");
        }
        n = 0;
        count = 0;
        // 读取 服务器返回的数据
        while (1) {
            n = read(sockfd, recvline + count, MAX_LINE);
            if (n == MAX_LINE) {
                count += n;
                continue;
            } else if (n < 0) {
                perror("recv");
                break;
            } else {
                count += n;
                recvline[count] = '\0';
                printf("[recv] %s\n", recvline);
                break;
            }
        }
    }
    return 0;
}