1 Linux 安装 Libevent

创建文件夹
chunli@Linux:~$ mkdir libevent
chunli@Linux:~$ cd libevent/

解压文件:
chunli@Linux:~/libevent$ tar xf libevent-2.0.22-stable.tar.gz
chunli@Linux:~/libevent$ cd libevent-2.0.22-stable/

编译环境检查:
chunli@Linux:~/libevent/libevent-2.0.22-stable$ ./configure
chunli@Linux:~/libevent/libevent-2.0.22-stable$ echo $?
0

编译:
chunli@Linux:~/libevent/libevent-2.0.22-stable$ make -j 8
chunli@Linux:~/libevent/libevent-2.0.22-stable$ echo $?
0

安装:
chunli@Linux:~/libevent/libevent-2.0.22-stable$ sudo make install
chunli@Linux:~/libevent/libevent-2.0.22-stable$ echo $?
0

删除临时文件:
chunli@Linux:~$ cd libevent/libevent-2.0.22-stable/
chunli@Linux:~/libevent/libevent-2.0.22-stable$ cd ..
chunli@Linux:~/libevent$ rm -rf libevent-2.0.22-stable
chunli@Linux:~/libevent$ echo $?
0

chunli@Linux:~/libevent$ cat hello-world.c
/*
This exmple program provides a trivial server program that listens for TCP
connections on port 9995.  When they arrive, it writes a short message to
each client connection, and closes each connection once it is flushed.

Where possible, it exits cleanly in response to a SIGINT (ctrl-c).
*/

#include <string.h>
#include <errno.h>
#include <stdio.h>
#include <signal.h>
#ifndef WIN32
#include <netinet/in.h>
# ifdef _XOPEN_SOURCE_EXTENDED
#  include <arpa/inet.h>
# endif
#include <sys/socket.h>
#endif

#include <event2/bufferevent.h>
#include <event2/buffer.h>
#include <event2/listener.h>
#include <event2/util.h>
#include <event2/event.h>

static const char MESSAGE[] = "Hello, World!\n";

static const int PORT = 9995;

static void listener_cb(struct evconnlistener *, evutil_socket_t,
struct sockaddr *, int socklen, void *);
static void conn_writecb(struct bufferevent *, void *);
static void conn_eventcb(struct bufferevent *, short, void *);
static void signal_cb(evutil_socket_t, short, void *);

int
main(int argc, char **argv)
{
struct event_base *base;
struct evconnlistener *listener;
struct event *signal_event;

struct sockaddr_in sin;
#ifdef WIN32
WSADATA wsa_data;
WSAStartup(0x0201, &wsa_data);
#endif

base = event_base_new();
if (!base) {
fprintf(stderr, "Could not initialize libevent!\n");
return 1;
}

memset(&sin, 0, sizeof(sin));
sin.sin_family = AF_INET;
sin.sin_port = htons(PORT);

listener = evconnlistener_new_bind(base, listener_cb, (void *)base,
LEV_OPT_REUSEABLE|LEV_OPT_CLOSE_ON_FREE, -1,
(struct sockaddr*)&sin,
sizeof(sin));

if (!listener) {
fprintf(stderr, "Could not create a listener!\n");
return 1;
}

signal_event = evsignal_new(base, SIGINT, signal_cb, (void *)base);

if (!signal_event || event_add(signal_event, NULL)<0) {
fprintf(stderr, "Could not create/add a signal event!\n");
return 1;
}

event_base_dispatch(base);

evconnlistener_free(listener);
event_free(signal_event);
event_base_free(base);

printf("done\n");
return 0;
}

static void
listener_cb(struct evconnlistener *listener, evutil_socket_t fd,
struct sockaddr *sa, int socklen, void *user_data)
{
struct event_base *base = user_data;
struct bufferevent *bev;

bev = bufferevent_socket_new(base, fd, BEV_OPT_CLOSE_ON_FREE);
if (!bev) {
fprintf(stderr, "Error constructing bufferevent!");
event_base_loopbreak(base);
return;
}
bufferevent_setcb(bev, NULL, conn_writecb, conn_eventcb, NULL);
bufferevent_enable(bev, EV_WRITE);
bufferevent_disable(bev, EV_READ);

bufferevent_write(bev, MESSAGE, strlen(MESSAGE));
}

static void
conn_writecb(struct bufferevent *bev, void *user_data)
{
struct evbuffer *output = bufferevent_get_output(bev);
if (evbuffer_get_length(output) == 0) {
printf("flushed answer\n");
bufferevent_free(bev);
}
}

static void
conn_eventcb(struct bufferevent *bev, short events, void *user_data)
{
if (events & BEV_EVENT_EOF) {
printf("Connection closed.\n");
} else if (events & BEV_EVENT_ERROR) {
printf("Got an error on the connection: %s\n",
strerror(errno));/*XXX win32*/
}
/* None of the other events can happen here, since we haven't enabled
* timeouts */
bufferevent_free(bev);
}

static void
signal_cb(evutil_socket_t sig, short events, void *user_data)
{
struct event_base *base = user_data;
struct timeval delay = { 2, 0 };

printf("Caught an interrupt signal; exiting cleanly in two seconds.\n");

event_base_loopexit(base, &delay);
}

编译运行:
chunli@Linux:~/libevent$ gcc hello-world.c -l event -Wall  && ./a.out

查看端口监听:
chunli@Linux:~$ sudo netstat -tanlp | grep a.out
tcp        0      0 0.0.0.0:9995            0.0.0.0:*               LISTEN      7740/a.out

本机IP
chunli@Linux:~$ ifconfig eth0
eth0      Link encap:以太网  硬件地址 00:0c:29:c8:7a:35
inet 地址:11.11.11.5  广播:11.11.11.255  掩码:255.255.255.0

----------------------------------

局域网其他机子访问测试:
pi@raspberrypi:~ $ nc 11.11.11.5 9995
Hello, World!
pi@raspberrypi:~ $ nc 11.11.11.5 9995
Hello, World!