下面是 hiredis 异步调用使用的一个例子（算是对于官方简单例子的一个补充，可能长得更像实际业务中使用的样子），一般使用场景是我们监听一个端口，当有请求来的时候，就执行回调，而回调里面可能需要读写 Redis。（涉及 IO 的操作都需要异步处理！）

#include <hiredis/hiredis.h>
#include <hiredis/adapters/libevent.h>
#include <sys/socket.h>

void do_accept(evutil_socket_t listener, short event, void *arg) {
    redisAsyncContext *ac = (redisAsyncContext *)arg;
    evutil_socket_t fd;
    struct sockaddr_in sin;
    socklen_t slen = sizeof(sin);
    fd = accept(listener, (struct sockaddr *)&sin, &slen);
    if (fd < 0) {
        perror("[ERROR] accept error");
        return;
    }
    redisAsyncCommand(ac, NULL, NULL, "SET key test");
}
int main() {
    signal(SIGPIPE, SIG_IGN);
    struct event_base *base = event_base_new();

    /* 创建套接字 */
    int listenfd;
    struct sockaddr_in servaddr;
    if ((listenfd = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
        printf("[ERROR] socket error");
        exit(-1);
    }

    bzero(&servaddr, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr.sin_port = htons(17777);

    bind(listenfd, (const struct sockaddr*) &servaddr, sizeof(servaddr));

    if (listen(listenfd, 1024) < 0) {
        printf("[ERROR] listen error");
        exit(-1);
    }


    redisAsyncContext *c = redisAsyncConnect("127.0.0.1", 6379);
    if (c->err) {
        /* Let *c leak for now... */
        printf("Error: %s\n", c->errstr);
        return 1;
    }

    redisLibeventAttach(c,base);
    c->data = (void *)base;

    struct event *listen_event;
    listen_event = event_new(base, listenfd, EV_READ|EV_PERSIST, do_accept, (void *)c);
    event_add(listen_event, NULL);

    event_base_dispatch(base);

    return 0;
}