libevent 框架使用例子

時間 2019-11-10

標籤 libevent 框架使用例子简体版

原文原文鏈接

//服務端代碼：編程

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

#include <arpa/inet.h>

#include <event.h>
#include <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 argc, char *argv[])
{
if( argc <= 1 )
{
printf( "usage: %s ip_address\n", basename( argv[0] ) );
return 1;
}

const char* ip = argv[1];

evutil_socket_t listener;//用於跨平臺表示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);
//用於跨平臺將socket設置爲可重用（其實是將端口設爲可重用)
evutil_make_listen_socket_reuseable(listener);

struct sockaddr_in sin;
bzero( &sin, sizeof( sin ) );
sin.sin_family = AF_INET;
//sin.sin_addr.s_addr = 0;
inet_pton( AF_INET, ip, &sin.sin_addr );
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");
/* 用於跨平臺將socket設置爲非阻塞,使用bufferevent須要 */
evutil_make_socket_nonblocking(listener);
//主要記錄事件的相關屬性建立一個event_base
struct event_base *base = event_base_new();
assert(base != NULL);
/* 建立並綁定一個event */
struct event *listen_event;
//參數：event_base, 監聽的socket 描述符listener，事件類型及屬性，綁定的回調函數，給回調函數的參數
/*EV_PERSIST參數告訴系統持續的監聽sock上的讀事件，
不指定這個屬性的話，回調函數被觸發後,事件會被刪除.因此,若是不加該參數，每次要監聽該事件時就要重複的調用event_add函數 */
listen_event = event_new(base, listener, EV_READ|EV_PERSIST, do_accept, (void*)base);
/*經過event_add方法啓動監聽事件
參數：event，超時時間(struct timeval *類型的，NULL表示無超時設置) */
event_add(listen_event, NULL);
/* 進入事件循環,即經過event_base_dispatch方法啓動事件循環 */
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) { //這個if是參考了那個ROT13的例子，貌似是官方的疏漏，從select-based例子裏抄過來忘了改
perror("fd > FD_SETSIZE\n");
return;
}

printf("ACCEPT: fd = %u\n", fd);
//關聯該sockfd，託管給event_base. BEV_OPT_CLOSE_ON_FREE--釋放bufferevent時關閉底層傳輸端口。這將關閉底層套接字，釋放底層bufferevent等。
struct bufferevent *bev = bufferevent_socket_new(base, fd, BEV_OPT_CLOSE_ON_FREE);
//設置讀寫對應的回調函數
bufferevent_setcb(bev, read_cb, NULL, error_cb, arg);
//啓用讀寫事件,實際上是調用了event_add將相應讀寫事件加入事件監聽隊列poll.
//若是相應事件不置爲true，bufferevent是不會讀寫數據的
bufferevent_enable(bev, EV_READ|EV_PERSIST);
// 進入bufferevent_setcb回調函數：
// 在read_cb裏面從input中讀取數據，處理完畢後填充到output中；
// write_cb對於服務端程序，只須要readcb就能夠了，能夠置爲NULL；
// error_cb用於處理一些錯誤信息
}

void read_cb(struct bufferevent *bev, void *arg)
{
char line[MAX_LINE+1];
int n;
//根據以前已經分配好的bufferevent 獲取對應的鏈接描述符
evutil_socket_t fd = bufferevent_getfd(bev);

while (n = bufferevent_read(bev, line, MAX_LINE), n > 0)
{
line[n] = '\0';
printf("fd=%u, Server gets the message from client read line: %s\n", fd, line);
//直接將讀取的結果,不作任何修改,直接返回給客戶端
bufferevent_write(bev, line, n);//方案1
}
}

void write_cb(struct bufferevent *bev, void *arg)
{
printf("HelloWorld\n");//直接空代碼便可，由於這裏並不會被觸發調用
}

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);
} socket

客戶端代碼：函數

//客戶端代碼 ui

//客戶端代碼
#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[])
{
if(argc < 2)
{
perror("usage: echocli <IPadress>");
return 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, argv[1], &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;
}
//獲取通訊模式：這裏爲epoll
const char *eventMechanism = event_base_get_method(base);
printf("Event mechanism used is %s\n", eventMechanism);
printf("sockfd = %d\n", sockfd);

//關聯該鏈接描述符sockfd，託管給event_base.
struct bufferevent *bev = bufferevent_socket_new(base, sockfd, BEV_OPT_CLOSE_ON_FREE);

//聲明事件
struct event *ev_cmd;
//建立一個用於監聽標準輸入的事件ev_cmd
ev_cmd = event_new(base, STDIN_FILENO, EV_READ | EV_PERSIST, cmd_msg_cb, (void *)bev);
//添加到事件隊列當中.至關於告訴處理IO的管家，當有個人事件到達時你發給我(調用cmd_msg_cb函數)
event_add(ev_cmd, NULL);

//設置讀寫對應的回調函數
bufferevent_setcb(bev, read_cb, NULL, error_cb, (void *)ev_cmd);
//使用bufferevent_enable(bev, EV_READ|EV_PERSIST)來啓用read事件
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[n] = '\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);
} 編碼