基于libevent实现了一个简单的echoclient。之前在网上看到的都是echoserver。这里演示一下使用libevent进行客户端编程的基本步骤。

先看代码：

[cpp]
#include "stdafx.h"
#include "event2/event.h"
#include "event2/util.h"

#define ECHO_PORT 8888
#define ECHO_SERVER "127.0.0.1"

struct echo_context{
struct event_base *base;
struct event *event_write;
struct event *event_read;
const char * echo_contents;
int echo_contents_len;
int recved;
};

void write_cb(evutil_socket_t sock, short flags, void * args)
{
struct echo_context *ec = (struct echo_context *)args;

int ret = send(sock, ec->echo_contents, ec->echo_contents_len, 0);
printf("connected, write to echo server: %d\n", ret);
event_add(ec->event_read, 0);
}

void read_cb(evutil_socket_t sock, short flags, void * args)
{
struct echo_context *ec = (struct echo_context *)args;
char buf[128];
int ret = recv(sock, buf, 128, 0);

printf("read_cb, read %d bytes\n", ret);
if(ret > 0)
{
ec->recved += ret;
buf[ret] = 0;
printf("recv:%s\n", buf);
}
else if(ret == 0)
{
printf("read_cb connection closed\n");
event_base_loopexit(ec->base, NULL);
return;
}
if(ec->recved < ec->echo_contents_len)
{
event_add(ec->event_read, 0);
}
}

static evutil_socket_t make_tcp_socket()
{
int on = 1;
evutil_socket_t sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);

evutil_make_socket_nonblocking(sock);
#ifdef WIN32
setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (const char *)&on, sizeof(on));
#else
setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, sizeof(on));
#endif

return sock;
}

static void echo_client(struct event_base *base)
{
evutil_socket_t sock = make_tcp_socket();
struct sockaddr_in serverAddr;
struct event * ev_write = 0;
struct event * ev_read = 0;
struct timeva l tv={10, 0};
struct echo_context *ec = (struct echo_context*)calloc(1, sizeof(struct echo_context));

serverAddr.sin_family = AF_INET;
serverAddr.sin_port = htons(ECHO_PORT);
#ifdef WIN32
serverAddr.sin_addr.S_un.S_addr = inet_addr(ECHO_SERVER);
#else
serverAddr.sin_addr.s_addr = inet_addr(ECHO_SERVER);
#endif
memset(serverAddr.sin_zero, 0x00, 8);

connect(sock, (struct sockaddr*)&serverAddr, sizeof(serverAddr));

ev_write = event_new(base, sock, EV_WRITE, write_cb, (void*)ec);
ev_read = event_new(base, sock, EV_READ , read_cb, (void*)ec);

ec->event_write = ev_write;
ec->event_read = ev_read;
ec->base = base;
ec->echo_contents = strdup("echo client tneilc ohce\n");
ec->echo_contents_len = strlen(ec->echo_contents);
ec->recved = 0;

event_add(ev_write, &tv);
}

int _tmain(int argc, _TCHAR* argv[])
{
struct event_base * base = 0;
#ifdef WIN32
WORD wVersionRequested;
WSADATA wsaData;

wVersionRequested = MAKEWORD(2, 2);

(void) WSAStartup(wVersionRequested, &wsaData);
#endif

base = event_base_new();
echo_client(base);
event_base_dispatch(base);
event_base_free(base);

return 0;
}

#include "stdafx.h"
#include "event2/event.h"
#include "event2/util.h"

#define ECHO_PORT 8888
#define ECHO_SERVER "127.0.0.1"