linux io 复用高级应用2：聊天室程序

客户端：

#define _GNU_SOURCE 1
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <assert.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <poll.h>
#include <fcntl.h>

#define BUFFER_SIZE 64

int main(int argc, char* argv[]) {
    if (argc <= 2) {
        printf("usage: %s ip_address port_number\n", basename(argv[0]));
        return 1;
    }
    const char* ip = argv[1];
    int port = atoi(argv[2]);

    struct sockaddr_in server_address;
    bzero(&server_address, sizeof(server_address));
    server_address.sin_family = AF_INET;
    inet_pton(AF_INET, ip, &server_address.sin_addr);
    server_address.sin_port = htons(port);

    int sockfd = socket(PF_INET, SOCK_STREAM, 0);
    assert(sockfd >= 0);
    if (connect(sockfd, (struct sockaddr*)&server_address, sizeof(server_address)) < 0) {
        printf("connection failed!\n");
        close(sockfd);
        return 1;
    }

    pollfd fds[2];
    // 0文件描述符为标准输入 注册可读事件POLLIN
    fds[0].fd = 0;
    fds[0].events = POLLIN;
    fds[0].revents = 0;

    // sockfd文件描述符为监听的端口 注册可读事件POLLIN和对方关闭连接事件POLLRDHUP
    fds[1].fd = sockfd;
    fds[1].events = POLLIN | POLLRDHUP;
    fds[1].revents = 0;

    char read_buf[BUFFER_SIZE];
    int pipefd[2];
    int ret = pipe(pipefd);
    assert(ret != -1);

    while (1) {
        ret = poll(fds, 2, -1);
        if (ret < 0) {
            printf("poll failure\n");
            break;
        }

        if (fds[1].revents & POLLRDHUP) {
            printf("server close the connection");
            break;
        } else if (fds[1].revents & POLLIN) {
            memset(read_buf, '\0', BUFFER_SIZE);
            recv(fds[1].fd, read_buf, BUFFER_SIZE - 1, 0);
            printf("%s\n", read_buf);
        }

        if (fds[0].revents & POLLIN) {
            // 零拷贝 0 -> sockfd
            ret = splice(0, NULL, pipefd[1], NULL, 32768, SPLICE_F_MORE | SPLICE_F_MOVE);
            ret = splice(pipefd[0], NULL, sockfd, NULL, 32768, SPLICE_F_MORE | SPLICE_F_MOVE);
        }
    }
    close(sockfd);
    return 0;
}

服务器：

#define _GNU_SOURCE 1
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <assert.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <fcntl.h>
#include <stdlib.h>
#include <poll.h>

#define USER_LIMIT 5
#define BUFFER_SIZE 64
#define FD_LIMIT 65535

struct client_data
{
    sockaddr_in address;
    char* write_buf;
    char buf[BUFFER_SIZE];
};

int setnonblocking(int fd)
{
    int old_option = fcntl(fd, F_GETFL);
    int new_option = old_option | O_NONBLOCK;
    fcntl(fd, F_SETFL, new_option);
    return old_option;
}

int main(int argc, char* argv[])
{
    if (argc <= 2) {
        printf("usage: %s ip_address portnumber\n", basename(argv[0]));
        return 1;
    }
    const char* ip = argv[1];
    int port = atoi(argv[2]);

    int ret = 0;
    struct sockaddr_in address;
    bzero(&address, sizeof(address));
    address.sin_family = AF_INET;
    inet_pton(AF_INET, ip, &address.sin_addr);
    address.sin_port = htons(port);

    int listenfd = socket(PF_INET, SOCK_STREAM, 0);
    assert(listenfd >= 0);

    ret = bind(listenfd, (struct sockaddr*)&address, sizeof(address));
    assert(ret != 1);

    ret = listen(listenfd, 5);
    assert(ret != -1);

    client_data* users = new client_data[FD_LIMIT];

    pollfd fds[USER_LIMIT + 1];
    int user_counter = 0;
    for (int i = 1; i <= USER_LIMIT; i++) {
        fds[i].fd = -1;
        fds[i].events = 0;
    }
    // 注册事件：监听端口是否可读或者出现错误
    fds[0].fd = listenfd;
    fds[0].events = POLLIN | POLLERR;
    fds[0].revents = 0;

    while (1) {
        ret = poll(fds, user_counter + 1, -1);
        if (ret < 0) {
            printf("poll failure\n");
            break;
        }

        for (int i = 0; i < user_counter + 1; i++) {
            if ((fds[i].fd == listenfd) && (fds[i].revents & POLLIN)) {
                struct sockaddr_in client_address;
                socklen_t client_addrlength = sizeof(client_address);
                int connfd = accept(listenfd, (struct sockaddr*)&client_address, &client_addrlength);

                if (connfd < 0) {
                    printf("errno is: %d\n", errno);
                    continue;
                }

                if (user_counter >= USER_LIMIT) {
                    const char* info = "too many users\n";
                    printf("%s", info);
                    send(connfd, info, strlen(info), 0);
                    close(connfd);
                    continue;
                }

                user_counter++;
                users[connfd].address = client_address;
                setnonblocking(connfd);
                // 用于和新连接进来的客户的交互的文件描述符connfd
                fds[user_counter].fd = connfd;
                fds[user_counter].events = POLLIN | POLLRDHUP | POLLERR;
                fds[user_counter].revents = 0;
                printf("comes a new user, now have %d users\n", user_counter);
            } else if (fds[i].revents & POLLERR) { // 某个和用户连接出错了
                printf("get an error from %d\n", fds[i].fd);
                char errors[100];
                memset(errors, '\0', 100);
                socklen_t length = sizeof(errors);
                if (getsockopt(fds[i].fd, SOL_SOCKET, SO_ERROR, &errors, &length) < 0) {
                    printf("get socket options failed]n");
                }
                continue;
            } else if (fds[i].revents & POLLRDHUP) { // 用户断开了连接
                users[fds[i].fd] = users[fds[user_counter].fd];
                close(fds[i].fd);
                fds[i] = fds[user_counter];
                i--;
                user_counter--;
                printf("a client left\n");
            } else if (fds[i].revents & POLLIN) { // 用户连接可读，表示用户发送了数据过来
                int connfd = fds[i].fd;
                memset(users[connfd].buf, '\0', BUFFER_SIZE);
                ret = recv(connfd, users[connfd].buf, BUFFER_SIZE - 1, 0);
                printf("get %d bytes of client data %s from %d\n", ret, users[connfd].buf, connfd);
                if (ret < 0) {
                    if (errno != EAGAIN) {
                        close(connfd);
                        users[fds[i].fd] = users[fds[user_counter].fd];
                        fds[i] = fds[user_counter];
                        i--;
                        user_counter--;
                    }
                } else if (ret == 0) { // 对方关闭了连接 此时有POLLHUP处理

                } else {
                    for (int j = 1; j <= user_counter; j++) {
                        if (fds[j].fd == connfd) {
                            continue;
                        }

                        fds[j].events |= ~POLLIN; // 原书这里是这样写的 目的为注销可读。但是本人认为应该是 &= ，下同。
                        fds[j].events |= POLLOUT;
                        users[fds[j].fd].write_buf = users[connfd].buf; // 其他用户的buf写上当前收到的某fd所发送的信息
                    }
                }
            } else if (fds[i].revents & POLLOUT) { // 用户连接可写，把buffer信息写进去
                int connfd = fds[i].fd;
                if (!users[connfd].write_buf) {
                    continue;
                }
                ret = send(connfd, users[connfd].write_buf, strlen(users[connfd].write_buf), 0);
                users[connfd].write_buf = NULL;
                fds[i].events |= ~POLLOUT;
                fds[i].events |= POLLIN;
            }
        }
    }
    delete[] users;
    close(listenfd);
    return 0;

}

演示结果：
服务器：

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客户端1:

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客户端2:

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reference：
linux高性能服务器编程——游双