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 1024struct 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。