libevent I/O示例
I/O示例使用一个windows平台上服务器/客户端的例子来演示。由于为了减少代码篇幅等各种由于本人懒而产生的原因,以下代码没有做错误处理以及有些小问题,但是我想应该不影响演示,大家多包涵。
服务器代码:
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#include <stdio.h> #define WIN32_LEAN_AND_MEAN #include <windows.h> #include <winsock2.h> #include "event.h" #include "event_struct.h" #include "evutil.h" #define PORT 4000 #define IP_ADDRESS "172.16.80.101" #define MEM_SIZE 1024 struct event_base* base;
struct sock_ev
{ struct event* read_ev;
struct event* write_ev;
char * buffer;
}; void release_sock_event( struct sock_ev* ev)
{ event_del(ev->read_ev);
free (ev->read_ev);
free (ev->write_ev);
free (ev->buffer);
free (ev);
return ;
} void on_write( int sock, short event, void * arg)
{ char * buffer = ( char *)arg;
send(sock, buffer, strlen (buffer), 0);
printf ( "on_write
" );
free (buffer);
return ;
} void on_read( int sock, short event, void * arg)
{ struct event* write_ev;
int size;
struct sock_ev* ev = ( struct sock_ev*)arg;
printf ( "on_read
" );
ev->buffer = ( char *) malloc (MEM_SIZE);
memset (ev->buffer, 0, MEM_SIZE);
size = recv(sock, ev->buffer, MEM_SIZE, 0);
printf ( "receive data:%s, size:%d
" , ev->buffer, size);
if (size == 0)
{
release_sock_event(ev);
close(sock);
return ;
}
event_assign(ev->write_ev, base, sock, EV_WRITE, on_write, ev->buffer);
event_add(ev->write_ev, NULL);
return ;
} void on_accept( int sock, short event, void * arg)
{ struct sockaddr_in cli_addr;
int fd, sin_size;
struct sock_ev* ev = ( struct sock_ev*) malloc ( sizeof ( struct sock_ev));
printf ( "on_accept
" );
ev->read_ev = ( struct event*) malloc ( sizeof ( struct event));
ev->write_ev = ( struct event*) malloc ( sizeof ( struct event));
sin_size = sizeof ( struct sockaddr_in);
fd = accept(sock, ( struct sockaddr*)&cli_addr, &sin_size);
event_assign(ev->read_ev, base, fd, EV_READ|EV_PERSIST, on_read, ev);
event_add(ev->read_ev, NULL);
return ;
} int main( int argc, char * argv[])
{ WSADATA ws;
SOCKET srvSock;
struct sockaddr_in sockAddr;
struct event ev_listen;
WSAStartup(MAKEWORD(2,2), &ws);
srvSock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
sockAddr.sin_family = AF_INET;
sockAddr.sin_addr.s_addr = inet_addr(IP_ADDRESS);
sockAddr.sin_port = htons(PORT);
memset (sockAddr.sin_zero, 0, sizeof (sockAddr.sin_zero));
bind(srvSock, ( struct sockaddr*)&sockAddr, sizeof (sockAddr));
listen(srvSock, 10);
base = event_base_new();
event_assign(&ev_listen, base, srvSock, EV_READ|EV_PERSIST, on_accept, NULL);
event_add(&ev_listen, NULL);
event_base_dispatch(base);
closesocket(srvSock);
WSACleanup();
return 0;
} |
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客户端代码:
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#include "stdafx.h" #include <stdio.h> #define WIN32_LEAN_AND_MEAN #include <windows.h> #include <winsock2.h> #include "event.h" #include "event_struct.h" #include "evutil.h" #define PORT 4000 #define IP_ADDRESS "172.16.80.101" int main( int argc, char * argv[])
{ WSADATA ws;
SOCKET cltSocket;
struct sockaddr_in sockAddr;
int Ret = 0;
WSAStartup(MAKEWORD(2,2), &ws);
cltSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
sockAddr.sin_family = AF_INET;
sockAddr.sin_addr.s_addr = inet_addr(IP_ADDRESS);
sockAddr.sin_port = htons(PORT);
memset (sockAddr.sin_zero, 0, sizeof (sockAddr.sin_zero));
connect(cltSocket,( struct sockaddr*)&sockAddr, sizeof (sockAddr));
//send
char SendBuffer[MAX_PATH] = "test" ;
Ret = send(cltSocket, SendBuffer, ( int ) strlen (SendBuffer), 0);
printf ( "send size=%d.
" , Ret);
//recv
char recvBuf[50] = {0};
if ( 0 > recv(cltSocket, recvBuf, 50, 0) )
{
printf ( "recv fail.
" );
return 0;
}
printf ( "%s
" , recvBuf);
while (1)
{
Sleep(1000);
}
closesocket(cltSocket);
WSACleanup();
return 0;
} |
服务器的功能主要是接收客户端发来的数据,并返回给客户端。
客户端的功能主要是连接服务器后向服务器发送数据,然后读取服务器发来的数据。
下面分下以下代码流程:
客户端就不分析了,都是老套路。
服务器端:
(1) 首先添加一个永久的读类型的事件,指定的文件描述符是我们监听的socket。当有客户端来connect,这个事件会触发,触发回调函数on_accept()。
(2) 在on_accept()中accept后,在新的文件描述符上添加一个永久的读事件,当文件操作符可读,调用on_read()读取。
(3) 在on_read()中为了将数据写会给客户端,添加了一个写事件,这次的写事件不是永久的,只会触发一次,因为我们只将读取到的数据回给客户端一次。当文件描述符可写,触发回调函数on_write()写入给客户端。
(4) On_write()写入数据。