c - recv() 未由 libevent 触发

Question

我正在尝试通过其管理套接字连接到本地 openvpn 客户端并查询其状态/状态。

我已经在 libevent 支持下实现了以下程序。

#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <event2/event.h>
#include <fcntl.h>
#include <string.h>

char message[1000], server_reply[2000];
struct event *ev, *ev1, *ev2;

int fd_set_blocking(int fd, int blocking)
{
    int flags = fcntl(fd, F_GETFL, 0);
    if (flags == -1) {
        return 0;
    }
    if (blocking) {
        flags &= ~O_NONBLOCK;
    } else {
        flags |= O_NONBLOCK;
    }
    return fcntl(fd, F_SETFL, flags) != -1;
}

void cb_func_hold_release(evutil_socket_t fd, short what, void *arg)
{
    int sock = *(int *)arg;
    struct timeval one_seconds = {1,0};
    printf("IN CB CONNECT\n");
    sprintf (message, "hold release\n");
    if (send (sock, message, strlen (message), 0) < 0) {
        printf("send failed\n");
    }
    event_add(ev1, NULL);
}

void cb_func_write(evutil_socket_t fd, short what, void *arg)
{
    int sock = *(int *)arg;
    printf("IN CB CHECKSTATUS\n");
    sprintf (message, "status\n");
    if (send (sock, message, strlen (message), 0) < 0) {
        printf("send failed\n");
    }
    /*
        int reclen = recv (sock, server_reply, 2000, 0);
        if (reclen < 0) {
            printf("recving failed");
        } else {
            if (reclen > 1) {
                server_reply[reclen-1] = '\0';
            }
            printf("SERVER REPLT< %s\n", server_reply);
        }
        if (strstr(message, "CONNECTED")) {
            printf("VPN CONNECTED");
        }
    */
    event_add(ev2, NULL);
    if (event_pending(ev2,EV_READ|EV_PERSIST, NULL)) {
        printf("ADDED READ EVENT\n");

    }
}

void cb_func_read(evutil_socket_t fd, short what, void *arg)
{
    int sock = *(int *)arg;
    printf("IN CB READ\n");
    int reclen = recv (sock, server_reply, 2000, 0);
    if (reclen < 0) {
        printf("recving failed");
    } else {
        if (reclen > 1) {
            server_reply[reclen-1] = '\0';
        }
        printf("SERVER REPLY %s\n", server_reply);
    }
    if (strstr(message, "CONNECTED")) {
        printf("VPN CONNECTED");
    }

}

int main(void)
{
    int flags;
    int mgmretry = 0;
    int sock = 0;
    struct sockaddr_in server;

    struct timeval five_seconds = {1,0};
    struct event_base *base = event_base_new();


    ev = event_new(base, sock, EV_TIMEOUT, cb_func_hold_release, &sock);
    ev1 = event_new(base, sock, EV_WRITE, cb_func_write, &sock);
    ev2 = event_new(base, sock, EV_READ, cb_func_read, &sock);

    sock = socket (AF_INET, SOCK_STREAM, 0);
    if (sock == -1) {
        printf("COUILD NOT CREATE SOCKET\n");
        exit(0);
    }

    fd_set_blocking(sock, 1);

    server.sin_addr.s_addr = inet_addr("127.0.0.1");
    server.sin_family = AF_INET;
    server.sin_port = htons (12345);

    if (connect (sock, (struct sockaddr *)&server, sizeof (server)) < 0) {
        printf("connecting failed\n");
        exit(0);
    }



    event_add(ev, &five_seconds);
    printf("DISPATCHING\n");
    event_base_dispatch(base);

}

问题是读取回调“cb_func_read”未被触发。我的期望是，在我从 cb_func_write() 向 vpn 发送“状态”消息后，会发回一些数据，这些数据应该会触发读取回调，但这并没有发生。

如果我在写回调(注释部分)中的 send() 之后直接使用 recv()，我可以打印从 openvpn 发送的响应，以便这两者之间的通信正常工作。

Answer 1

除非您使用 event_add() 武装它，否则该事件不会触发。

您仅对 ev 事件执行了此操作，但未对 ev1 和 ev2 执行此操作。