libevent for echo server and client

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <assert.h>
#include <unistd.h>
#include <string.h>

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

#define LISTEN_PORT 9999
#define LISTEN_BACKLOG 32
#define MAX_LINE    256

void do_accept(evutil_socket_t listener, short event, void *arg);
void read_cb(struct bufferevent *bev, void *arg);
void error_cb(struct bufferevent *bev, short event, void *arg);
void write_cb(struct bufferevent *bev, void *arg);

int main()
{
//int ret;
evutil_socket_t listener;//用于跨平台表示socket的ID（在Linux下表示的是其文件描述符）
listener = socket(AF_INET, SOCK_STREAM, 0);
assert(listener > 0);
//用于跨平台将socket设置为可重用（实际上是将端口设为可重用
evutil_make_listen_socket_reuseable(listener);

struct sockaddr_in sin;
sin.sin_family = AF_INET;
sin.sin_addr.s_addr = inet_addr("127.0.0.1");
sin.sin_port = htons(LISTEN_PORT);

if (bind(listener, (struct sockaddr *)&sin, sizeof(sin)) < 0) {
perror("bind");
return 1;
}

if (listen(listener, LISTEN_BACKLOG) < 0) {
perror("listen");
return 1;
}

printf ("Listening...\n");
/* 用于跨平台将socket设置为非阻塞,使用bufferevent需要 */
evutil_make_socket_nonblocking(listener);
//主要记录事件的相关属性
struct event_base *base = event_base_new();
assert(base != NULL);
/* Register listen event. */
struct event *listen_event;
listen_event = event_new(base, listener, EV_READ|EV_PERSIST, do_accept, (void*)base);
event_add(listen_event, NULL);
/* Start the event loop. */
event_base_dispatch(base);

printf("The End.");
//close(listener);
return 0;
}

void do_accept(evutil_socket_t listener, short event, void *arg)
{
struct event_base *base = (struct event_base *)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("accept");
return;
}
if (fd > FD_SETSIZE) { //这个if是参考了那个ROT13的例子，貌似是官方的疏漏，从select-based例子里抄过来忘了改
perror("fd > FD_SETSIZE\n");
return;
}

printf("ACCEPT: fd = %u\n", fd);
//关联该sockfd，托管给event_base.
struct bufferevent *bev = bufferevent_socket_new(base, fd, BEV_OPT_CLOSE_ON_FREE);
//设置读写对应的回调函数
bufferevent_setcb(bev, read_cb, NULL, error_cb, arg);
//启用读写事件,其实是调用了event_add将相应读写事件加入事件监听队列poll.
//如果相应事件不置为true，bufferevent是不会读写数据的
bufferevent_enable(bev, EV_READ|EV_PERSIST);
//    进入bufferevent_setcb回调函数：
//    在readcb里面从input中读取数据，处理完毕后填充到output中；
//    writecb对于服务端程序，只需要readcb就可以了，可以置为NULL；
//    errorcb用于处理一些错误信息
}

void read_cb(struct bufferevent *bev, void *arg)
{
char line[MAX_LINE+1];
int n;
evutil_socket_t fd = bufferevent_getfd(bev);

while (n = bufferevent_read(bev, line, MAX_LINE), n > 0)
{
line
= '\0';
printf("fd=%u, Server gets the message from client read line: %s\n", fd, line);
//直接将读取的结果,不做任何修改(本文是跳过前两个字符),直接返回给客户端
bufferevent_write(bev, line, n);//方案1
}
}

void write_cb(struct bufferevent *bev, void *arg)
{
printf("HelloWorld\n");//直接空代码即可，因为这里并不会被触发调用
}

void error_cb(struct bufferevent *bev, short event, void *arg)
{
evutil_socket_t fd = bufferevent_getfd(bev);
printf("fd = %u, ", fd);
if (event & BEV_EVENT_TIMEOUT) {
printf("Timed out\n"); //if bufferevent_set_timeouts() called
}
else if (event & BEV_EVENT_EOF) {
printf("connection closed\n");
}
else if (event & BEV_EVENT_ERROR) {
printf("some other error\n");
}
bufferevent_free(bev);
}

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

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

#define SERV_PORT 9999
#define MAX_LINE 1024

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

int main(int argc, char *argv[])
{
char* ip_str = "127.0.0.1";

evutil_socket_t sockfd;
if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0)
{
perror("socket\n");
return 1;
}

struct sockaddr_in servaddr;
bzero(&servaddr, sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_port = htons(SERV_PORT);
if(inet_pton(AF_INET, ip_str, &servaddr.sin_addr) < 1)
{
perror("inet_ntop\n");
return 1;
}
if(connect(sockfd, (struct sockaddr *) &servaddr, sizeof(servaddr)) < 0)
{
perror("connect\n");
return 1;
}
evutil_make_socket_nonblocking(sockfd);

printf("Connect to server sucessfully!\n");
// build event base
struct event_base *base = event_base_new();
if(base == NULL)
{
perror("event_base\n");
return 1;
}
const char *eventMechanism = event_base_get_method(base);
printf("Event mechanism used is %s\n", eventMechanism);
printf("sockfd = %d\n", sockfd);

struct bufferevent *bev = bufferevent_socket_new(base, sockfd, BEV_OPT_CLOSE_ON_FREE);

struct event *ev_cmd;
ev_cmd = event_new(base, STDIN_FILENO, EV_READ | EV_PERSIST, cmd_msg_cb, (void *)bev);
event_add(ev_cmd, NULL);

bufferevent_setcb(bev, read_cb, NULL, error_cb, (void *)ev_cmd);
bufferevent_enable(bev, EV_READ | EV_PERSIST);

event_base_dispatch(base);

printf("The End.");
return 0;
}

void cmd_msg_cb(int fd, short event, void *arg)
{
char msg[MAX_LINE];
int nread = read(fd, msg, sizeof(msg));
if(nread < 0)
{
perror("stdio read fail\n");
return;
}

struct bufferevent *bev = (struct bufferevent *)arg;
bufferevent_write(bev, msg, nread);
}

void read_cb(struct bufferevent *bev, void *arg)
{
char line[MAX_LINE + 1];
int n;
evutil_socket_t fd = bufferevent_getfd(bev);

while((n = bufferevent_read(bev, line, MAX_LINE)) > 0)
{
line
= '\0';
printf("fd = %u, read from server: %s", fd, line);
}
}

void error_cb(struct bufferevent *bev, short event, void *arg)
{
evutil_socket_t fd = bufferevent_getfd(bev);
printf("fd = %u, ", fd);
if(event & BEV_EVENT_TIMEOUT)
printf("Time out.\n");  // if bufferevent_set_timeouts() is called
else if(event & BEV_EVENT_EOF)
printf("Connection closed.\n");
else if(event & BEV_EVENT_ERROR)
printf("Some other error.\n");
bufferevent_free(bev);

struct event *ev = (struct event *)arg;
event_free(ev);
}