libevent(2) : 用libevent改写server端 实现echo_server

(1) echo_server.c

listen_event的callback函数是 do_accept_cb

bev (buffer event)的三个callback函数：read_cb, write_cb, error_cb。 本例中，server端无需write_cb函数

#include <stdio.h>
#include <stdlib.h>
#include <strings.h>
#include <errno.h>
#include <assert.h>

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

#define LISTEN_PORT 9999
#define LISTEN_BACKLOG 32

#define oops(msg) { perror(msg); exit(EXIT_FAILURE); }

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
= '\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);
}

void do_accept_cb(evutil_socket_t sockfd, short event_type, void *arg){
evutil_socket_t fd;
struct sockaddr_in sin;
socklen_t slen;

fd = accept(sockfd, (struct sockaddr *)&sin, &slen);
if (fd < 0) oops("ERROR: accept: ");
if (fd > FD_SETSIZE) oops("ERROR: fd > FD_SETSIZE");

printf("ACCEPT: fd = %u\n", fd);

struct event_base *base;
base = (struct event_base *)arg;
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);
}

int main(int argc, char **argv){
evutil_socket_t socket_fd;
socket_fd = socket(PF_INET, SOCK_STREAM, 0);
assert(socket_fd > 0);
if(socket_fd == -1) oops("ERROR: socket initiate:");
evutil_make_listen_socket_reuseable(socket_fd);

struct sockaddr_in address;
bzero((void *)&address, sizeof(address));
address.sin_family = AF_INET;
address.sin_addr.s_addr = inet_addr("172.16.166.129");
//	address.sin_addr.s_addr = 0;
address.sin_port =  htons(LISTEN_PORT);

int bind_return =  bind(socket_fd, (struct sockaddr *)&address, sizeof(address));
if(bind_return == -1) oops("ERROR: bind:");

int listen_return = listen(socket_fd, LISTEN_BACKLOG);
if(listen_return == -1) oops("ERROR: listen:");

//================================================
puts("Listening...");
evutil_make_socket_nonblocking(socket_fd);

struct event_base *base;
struct event *listen_event;

base = event_base_new();
assert(base != NULL);
if(base == NULL) oops("ERROR: event_base_new() :");
listen_event = event_new(base, socket_fd, EV_READ|EV_PERSIST, do_accept_cb, (void*)base);
event_add(listen_event, NULL); //NULL: no timeout
event_base_dispatch(base);

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

(2) echo_client.c

一个普通的client端，没有用libevent.

改进方法：可以设置buffer_event, 然后实现write_cb函数和error_cb函数。

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

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

#define oops(msg) { perror(msg); exit(EXIT_FAILURE); }
#define SIZE 256

#define LISTEN_PORT 9999

int main(){
int socket_fd = socket(PF_INET, SOCK_STREAM, 0);
if(socket_fd == -1) oops("socket initiating error...");

struct sockaddr_in address;
bzero(&address, sizeof(address));
address.sin_family = AF_INET;
address.sin_addr.s_addr = inet_addr("172.16.166.129");
//        address.sin_addr.s_addr = 0;
address.sin_port =  htons(LISTEN_PORT);

int connect_result = connect(socket_fd, (struct sockaddr*)&address, sizeof(address));
if(connect_result == -1) oops("connect error...");

char buffer[] = "hello world";
ssize_t write_length = write(socket_fd, buffer, strlen(buffer)+1); //write to socket_fd
if(write_length != (strlen(buffer)+1)) oops("error: write ...");

ssize_t read_length = read(socket_fd, buffer, strlen(buffer)+1);
if(read_length == -1) oops("error: read data from socket...");

printf("the ret msg is: %s\n", buffer);

close(socket_fd);
return EXIT_SUCCESS;
}

3. Makefile.am

AM_CPPFLAGS = -I/usr/local/include
LDADD = -L/usr/local/lib -levent

bin_PROGRAMS = echo-server echo-client
echo_server_SOURCES = echo_server.c
echo_client_SOURCES = echo_client.c