初识Libevent

libevent是用c写的高并发网络io库，只要有文件描述符，就都可使用libevent。

libevent使用回调函数（callback）。

有了libevent，网络编程我有

1, FIFO的进程间通信。

利用FIFO的进程间通信read端：

#include <event2/event.h>

#include <unistd.h>

#include <sys/types.h>

#include <sys/stat.h>

#include <fcntl.h>

#define MYFIFO "myfifo"

//call back

void readcb(evutil_socket_t fd, short what, void* arg){

  //read fifo

  char buf[24] = {0};

  int len = read(fd, buf, sizeof(buf));

  buf[len] = '\0';

  printf("data len = %d, buf = %s\n", len, buf);

  printf("read event:%s\n", what & EV_READ ? "Yes" : "No");

}

int main(){

  unlink(MYFIFO);

  mkfifo(MYFIFO, 0664);

  int fd = open(MYFIFO, O_RDONLY | O_NONBLOCK);

  //int fd = open(MYFIFO, O_RDONLY);

  struct event_base* base;

  base = event_base_new();

  //create event

  struct event* ev = NULL;

  ev = event_new(base, fd, EV_READ | EV_PERSIST | EV_ET, readcb, NULL);

  //add event

  event_add(ev, NULL);

  //start

  event_base_dispatch(base);

  //free event

  event_free(ev);

  event_base_free(base);

  close(fd);

  return 0;

}

利用FIFO的进程间通信write端：

#include <event2/event.h>

#include <unistd.h>

#include <sys/types.h>

#include <sys/stat.h>

#include <fcntl.h>

#include <string.h>

#define MYFIFO "myfifo"

//call back

void writecb(evutil_socket_t fd, short what, void* arg){

  //write fifo

  char buf[24] = {0};

  static int num = 0;

  sprintf(buf, "num = %d", num++);

  write(fd, buf, strlen(buf) + 1);

}

int main(){

  int fd = open(MYFIFO, O_WRONLY | O_NONBLOCK);

  struct event_base* base;

  base = event_base_new();

  //create event

  struct event* ev = NULL;

  ev = event_new(base, fd, EV_WRITE | EV_PERSIST | EV_ET, writecb, NULL);

  //add event

  event_add(ev, NULL);

  //start

  event_base_dispatch(base);

  //free event

  event_free(ev);

  event_base_free(base);

  close(fd);

  return 0;

}

2, socket通信。

server端：

#include <event2/event.h>

#include <unistd.h>

#include <sys/types.h>

#include <sys/stat.h>

#include <fcntl.h>

#include <event2/bufferevent.h>

#include <arpa/inet.h>

#include <stdlib.h>

#include <event2/listener.h>

//write callback

void write_cb(struct bufferevent* bev, void* ctx){

  printf("all is sent\n");

}

//read callback

void read_cb(struct bufferevent *bev, void *ctx){

  char buf[64];

  size_t ret = bufferevent_read(bev, buf, sizeof(buf));

  buf[ret] = '\0';

  printf("server recf:%s\n", buf);

  bufferevent_write(bev, "hahaha", 6);

}

//event callback

void event_cb(struct bufferevent *bev, short what, void *ctx){

  if(what & BEV_EVENT_EOF){

    printf("EOF\n");

  }

  if(what & BEV_EVENT_CONNECTED){

    printf("connected\n");

  }

}

//listener call back

void listencb(struct evconnlistener* listener, evutil_socket_t fd,

	      struct sockaddr* cli, int len, void* ptr){

  struct event_base* base = evconnlistener_get_base(listener);

  struct bufferevent* bev =

    bufferevent_socket_new(base, fd, BEV_OPT_CLOSE_ON_FREE);

  //set callback function

  bufferevent_setcb(bev, read_cb, write_cb, event_cb, NULL);

  bufferevent_enable(bev, EV_READ | EV_WRITE);

  //set water

  bufferevent_setwatermark(bev, EV_READ, 10, 0);

  bufferevent_setwatermark(bev, EV_WRITE, 1, 2);

}

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

  int port = atoi(argv[1]);

  struct event_base* base;

  base = event_base_new();

  if(!base){

    perror("event_base_new");

    exit(1);

  }

  struct sockaddr_in s;

  s.sin_family = AF_INET;

  s.sin_port = htons(port);

  s.sin_addr.s_addr = htonl(INADDR_ANY);

  struct evconnlistener* listener =

    evconnlistener_new_bind(base, listencb, NULL, LEV_OPT_CLOSE_ON_FREE,

			    -1, (struct sockaddr*)&s, sizeof(s));

  if(!listener){

    perror("bind");

    exit(1);

  }

  event_base_dispatch(base);

  event_base_free(base);

}

client端:

#include <event2/event.h>

#include <unistd.h>

#include <sys/types.h>

#include <sys/stat.h>

#include <fcntl.h>

#include <event2/bufferevent.h>

#include <arpa/inet.h>

#include <stdlib.h>

#include <event2/listener.h>

#include <event2/dns.h>

#include <stdlib.h>

#include <event2/util.h>

//read write callback

void readcb(struct bufferevent *bev, void *ctx){

  char buf[64];

  size_t ret = bufferevent_read(bev, buf, sizeof(buf));

  buf[ret] = '\0';

  printf("client recf:%s\n", buf);

}

//event callback

void eventcb(struct bufferevent *bev, short what, void *ctx){

  if(what & BEV_EVENT_CONNECTED){

    printf("connect okay\n");

  }

  else if(what & BEV_EVENT_ERROR){

    struct event_base* base = ctx;

    int err = bufferevent_socket_get_dns_error(bev);

    if(err){

      printf("DNS error:%s\n", evutil_gai_strerror(err));

    }

    printf("closing\n");

    bufferevent_free(bev);

    event_base_loopexit(base, NULL);

  }

}

//terminal read callback

void termicb(evutil_socket_t fd, short what, void* ptr){

  char buf[64] = {0};

  int len = read(fd, buf, sizeof(buf));

  buf[len] = '\0';

  printf("in termicb\n");

  struct bufferevent* bev = ptr;

  bufferevent_write(bev, buf, len);

}

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

  struct event_base* base;

  base = event_base_new();

  struct evdns_base* dns_base;

  dns_base = evdns_base_new(base, 1);

  struct bufferevent* bev;

  bev = bufferevent_socket_new(base, -1, BEV_OPT_CLOSE_ON_FREE);

  int port = atoi(argv[2]);

  bufferevent_setcb(bev, readcb, NULL, eventcb, base);

  bufferevent_enable(bev, EV_READ);

  bufferevent_socket_connect_hostname(bev, dns_base, AF_INET, argv[1], port);

  struct event* ev = event_new(base, STDIN_FILENO, EV_READ | EV_PERSIST, termicb, bev);

  event_add(ev, NULL);

  event_base_dispatch(base);

  event_base_free(base);

}

巴特西

Linux 初识Libevent网络库

初识Libevent

有了libevent，网络编程我有

1, FIFO的进程间通信。

2, socket通信。

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