libevent编写echo服务器-蒲公英云

libevent编写echo服务器

为了使用libevent，编写一个echo回射服务器程序。

1. 准备工作

在深入浅出Libevent一书上提到，如果是源码学习的话使用libevent1.4版本，如果是使用的话一般用libevent2.x版本。
因此，在libevent.org上将libevent2.0.20-stable版本的源码下载下来，编译，安装：

./configure --prefix=INSTALL_DIR
make
make install

2. 编写Makefile

在Makefile中，需要指定libevent安装的头文件目录（gcc中-I选项）和库文件目录（gcc中-L选项），以及加上编译标志-levent

PROGS=echo 
CLEANFILES = core core.* *.core *.o temp.* *.out typescript* \
        *.lc *.lh *.bsdi *.sparc *.uw
LIBEVENT_DIRECTORY = /home/zhangxiao/libevent/src/src2 ### INSTALL DIR
LIBEVENT_INCLUDE = $(LIBEVENT_DIRECTORY)/include
LIBEVENT_LIBRARY = $(LIBEVENT_DIRECTORY)/lib
SRC=${shell pwd}/src
OUTPUT:=${shell pwd}/bin
MAKE_BIN_DIR := ${shell mkdir -p $(OUTPUT) }
all : ${PROGS}
CFLAGS+=-g  -I${LIBEVENT_INCLUDE} 
LDFLAGS+=-L${LIBEVENT_LIBRARY} -levent -lpthread -lrt
echo:${SRC}/echo.o
    @${CC} ${CFLAGS}  -o ${OUTPUT}/$@   $^  ${LDFLAGS}
clean:
    @rm -rf ${OUTPUT} \
        @rm -rf ${SRC}/*.o
.PHONY: all clean

3. 编写echo server

由于libevent的Reactor设计模式，我们需要为网络事件编写回调函数（Handler），例如onAccept,onRead等等

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <assert.h>
#include <event2/event.h>
#include <event2/bufferevent.h>
#define LISTEN_PORT 9999
#define LISTEN_BACKLOG 32
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)
{
    int ret;
    evutil_socket_t listener;
    listener=socket(AF_INET,SOCK_STREAM,0);
    assert(listener>0);
    evutil_make_listen_socket_reuseable(listener);
    struct sockaddr_in sin;
    sin.sin_family=AF_INET;
    sin.sin_addr.s_addr=0;
    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...\r\n");
    evutil_make_socket_nonblocking(listener);
    struct event_base *base = event_base_new();
    assert(base != NULL);
    struct event *listen_event;
    listen_event = event_new(base, //base
        listener, //fd
        EV_READ|EV_PERSIST,//event
        do_accept, //call back
        (void*)base);//args
    event_add(listen_event,NULL);
    event_base_dispatch(base);
    printf("The End.\r\n");
    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);
    struct bufferevent *bev = bufferevent_socket_new(base, fd, BEV_OPT_CLOSE_ON_FREE);
    bufferevent_setcb(bev, read_cb, NULL, error_cb, arg);
    bufferevent_enable(bev, EV_READ|EV_WRITE|EV_PERSIST);
}
void read_cb(struct bufferevent *bev, void *arg)
{
#define MAX_LINE    256
    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[n] = '\0';
    printf("fd=%u, read line: %s\n", fd, line);
    bufferevent_write(bev, line, n);
    }
}
void write_cb(struct bufferevent *bev, void *arg) {}
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);
}