【Networking】Libevent客户端例子

[原]Libevent客户端例子
时间 -- ::  luotuo44的专栏
原文  http://blog.****.net/luotuo44/article/details/34416429
主题 libevent Socket
网上关于Libevent的例子大多数都是服务器端的例子，我写一个客户端例子和大家分享。不多说了，上代码。

#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<arpa/inet.h>
#include<errno.h>
#include<unistd.h>

#include<stdio.h>
#include<string.h>
#include<stdlib.h>

#include<event.h>
#include<event2/bufferevent.h>
#include<event2/buffer.h>
#include<event2/util.h>

int tcp_connect_server(const char* server_ip, int port);

void cmd_msg_cb(int fd, short events, void* arg);
void server_msg_cb(struct bufferevent* bev, void* arg);
void error_cb(struct bufferevent *bev, short event, void *arg);

int main(int argc, char** argv)
{
  if( argc <  )
  {
    printf("please input 2 parameter\n");
    return -;
  }

  //两个参数依次是服务器端的IP地址、端口号
  int sockfd = tcp_connect_server(argv[], atoi(argv[]));
  if( sockfd == -)
  {
    perror("tcp_connect error ");
    return -;
  }

  printf("connect to server successful\n");

  struct event_base* base = event_base_new();

  struct bufferevent* bev = bufferevent_socket_new(base, sockfd,
                           BEV_OPT_CLOSE_ON_FREE);
  bufferevent_setcb(bev, server_msg_cb, NULL, error_cb, NULL);
  bufferevent_enable(bev, EV_READ | EV_PERSIST);

  //监听终端输入事件
  struct event* ev_cmd = event_new(base, STDIN_FILENO,
                    EV_READ | EV_PERSIST, cmd_msg_cb,
                    (void*)bev);

  event_add(ev_cmd, NULL);

  event_base_dispatch(base);

  printf("finished \n");
  return ;
}

void cmd_msg_cb(int fd, short events, void* arg)
{
  char msg[];

  int ret = read(fd, msg, sizeof(msg));
  if( ret <  )
  {
    perror("read fail ");
    exit();
  }

  struct bufferevent* bev = (struct bufferevent*)arg;

  //把终端的消息发送给服务器端
  bufferevent_write(bev, msg, ret);
}

void server_msg_cb(struct bufferevent* bev, void* arg)
{
  char msg[];

  size_t len = bufferevent_read(bev, msg, sizeof(msg));
  msg[len] = '\0';

  printf("recv %s from server\n", msg);
}

void error_cb(struct bufferevent *bev, short event, void *arg)
{

  if (event & BEV_EVENT_EOF)
    printf("connection closed\n");
  else if (event & BEV_EVENT_ERROR)
    printf("some other error\n");

  //这将自动close套接字和free读写缓冲区
  bufferevent_free(bev);
}

typedef struct sockaddr SA;
int tcp_connect_server(const char* server_ip, int port)
{
  int sockfd, status, save_errno;
  struct sockaddr_in server_addr;

  memset(&server_addr, , sizeof(server_addr) );

  server_addr.sin_family = AF_INET;
  server_addr.sin_port = htons(port);
  status = inet_aton(server_ip, &server_addr.sin_addr);

  if( status ==  ) //the server_ip is not valid value
  {
    errno = EINVAL;
    return -;
  }

  sockfd = ::socket(PF_INET, SOCK_STREAM, );
  if( sockfd == - )
    return sockfd;

  status = ::connect(sockfd, (SA*)&server_addr, sizeof(server_addr) );

  if( status == - )
  {
    save_errno = errno;
    ::close(sockfd);
    errno = save_errno; //the close may be error
    return -;
  }

  evutil_make_socket_nonblocking(sockfd);

  return sockfd;
}
        在main函数里面，要先connect上服务器，然后用套接字作为参数，新建一个struct buffereven。

我试过像下面这样写

struct bufferevent* bev = bufferevent_socket_new(base, -,
                           BEV_OPT_CLOSE_ON_FREE);
  if( bev == NULL)
  {
    printf("bufferevent_socket_new fail\n");
    return -;
  }

  struct sockaddr_in server_addr;

  memset(&server_addr, , sizeof(server_addr) );

  server_addr.sin_family = AF_INET;
  server_addr.sin_port = htons(atoi(argv[]));
  int status = inet_aton(argv[], &server_addr.sin_addr);

  int sockfd = bufferevent_socket_connect(bev, (struct sockaddr *)&server_addr,
                      sizeof(server_addr));
        即通过bufferevent_socket_connect函数来获取一个连接上服务器的套接字。但总会一连上服务器端，sockfd就关闭了。

下面是对应服务器端的例子。

#include<stdio.h>
#include<string.h>
#include<errno.h>

#include<event.h>
#include<event2/bufferevent.h>

void accept_cb(int fd, short events, void* arg);
void socket_read_cb(bufferevent* bev, void* arg);
void error_cb(struct bufferevent *bev, short event, void *arg);
int tcp_server_init(int port, int listen_num);

int main(int argc, char** argv)
{

  int listener = tcp_server_init(, );
  if( listener == - )
  {
    perror(" tcp_server_init error ");
    return -;
  }

  struct event_base* base = event_base_new();

  //添加监听客户端请求连接事件
  struct event* ev_listen = event_new(base, listener, EV_READ | EV_PERSIST,
                    accept_cb, base);
  event_add(ev_listen, NULL);

  event_base_dispatch(base);

  return ;
}

void accept_cb(int fd, short events, void* arg)
{
  evutil_socket_t sockfd;

  struct sockaddr_in client;
  socklen_t len;

  sockfd = ::accept(fd, (struct sockaddr*)&client, &len );
  evutil_make_socket_nonblocking(sockfd);

  printf("accept a client %d\n", sockfd);

  struct event_base* base = (event_base*)arg;

  bufferevent* bev = bufferevent_socket_new(base, sockfd, BEV_OPT_CLOSE_ON_FREE);
  bufferevent_setcb(bev, socket_read_cb, NULL, error_cb, arg);

  bufferevent_enable(bev, EV_READ | EV_PERSIST);
}

void socket_read_cb(bufferevent* bev, void* arg)
{
  char msg[];

  size_t len = bufferevent_read(bev, msg, sizeof(msg));

  msg[len] = '\0';
  printf("recv the client msg: %s", msg);

  char reply_msg[] = "I have recvieced the msg: ";

  strcat(reply_msg + strlen(reply_msg), msg);
  bufferevent_write(bev, reply_msg, strlen(reply_msg));
}

void error_cb(struct bufferevent *bev, short event, void *arg)
{

  if (event & BEV_EVENT_EOF)
    printf("connection closed\n");
  else if (event & BEV_EVENT_ERROR)
    printf("some other error\n");

  //这将自动close套接字和free读写缓冲区
  bufferevent_free(bev);
}

typedef struct sockaddr SA;
int tcp_server_init(int port, int listen_num)
{
  int errno_save;
  evutil_socket_t listener;

  listener = ::socket(AF_INET, SOCK_STREAM, );
  if( listener == - )
    return -;

  //允许多次绑定同一个地址。要用在socket和bind之间
  evutil_make_listen_socket_reuseable(listener);

  struct sockaddr_in sin;
  sin.sin_family = AF_INET;
  sin.sin_addr.s_addr = ;
  sin.sin_port = htons(port);

  if( ::bind(listener, (SA*)&sin, sizeof(sin)) <  )
    goto error;

  if( ::listen(listener, listen_num) < )
    goto error;

  //跨平台统一接口，将套接字设置为非阻塞状态
  evutil_make_socket_nonblocking(listener);

  return listener;

  error:
    errno_save = errno;
    evutil_closesocket(listener);
    errno = errno_save;

    return -;
}

参考资料：

http://www.tuicool.com/articles/uuQvai

http://blog.****.net/nanjunxiao/article/details/9066077

http://blog.****.net/lulyon/article/details/51259109

http://cnodejs.org/topic/506d524c01d0b80148be69d8

https://www.zhihu.com/question/20278441