网站图怎么做才能小而清晰白杨seo教程
一、介绍
1.为什么需要reactor网络模型
1.1 高并发支持
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非阻塞I/O：Reactor模型通过非阻塞I/O操作，允许单线程处理多个连接，减少线程切换开销，提升并发能力。
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事件驱动：基于事件驱动机制，系统只在有事件发生时处理，避免忙等待，提高资源利用率。
1.2 资源高效
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减少线程开销：传统多线程模型中，每个连接需要一个线程，Reactor模型通过少量线程处理多个连接，降低线程创建和上下文切换的开销。
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内存占用低：由于线程数减少，内存占用也相应降低，适合资源受限的环境。
1.3 可扩展性强
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模块化设计：Reactor模型将事件分发与处理逻辑分离，便于扩展和维护。
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支持多种I/O多路复用：如select、poll、epoll等，适应不同平台和需求。
1.4 响应迅速
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低延迟：事件驱动机制确保事件能快速响应，减少等待时间，提升系统响应速度。
1.5 简化编程
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统一事件处理：所有事件通过同一接口处理，简化编程模型，降低复杂度。
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避免竞态条件：单线程或少量线程处理事件，减少多线程环境下的竞态问题。
1.6 适用场景广泛
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高并发服务器：如Web服务器、游戏服务器等。
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实时系统：如即时通讯、在线交易等低延迟场景。
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分布式系统：如消息队列、RPC框架等。
2.实现思路
根据不同的io事件，调用不同的回调函数
io event callback
listenfd EPOLLIN accept_cb
clientfd EPOLLIN recv_cb
clientfd EPOLLOUT send_cb
二、代码
1.创建服务端
int initserver(int port){int sockfd = socket(AF_INET, SOCK_STREAM, 0);struct sockaddr_in servaddr;memset(&servaddr, 0, sizeof(servaddr));servaddr.sin_family = AF_INET;servaddr.sin_addr.s_addr = htonl(INADDR_ANY);servaddr.sin_port = htons(port);if(-1 == bind(sockfd, (struct sockaddr*)&servaddr, sizeof(struct sockaddr))){perror("bind failed!");printf("bind failed!");}listen(sockfd, 10);return sockfd;}对传入的端口进行绑定
2.创建epoll
创建一个io的一个结构体，定义io的连接数量
struct conn{int fd;char rbuffer[BUFFERLENGTH];int rbufferlength;char wbuffer[BUFFERLENGTH];int wbufferlength;CALLBACK send_callback;union {CALLBACK accept_callback;CALLBACK recv_callback;}r_action;
};struct conn conn_list[CONNECTIONSIZE] = {0};
创建epoll将服务端的fd加入到epoll中，并设置事件类型
epfd = epoll_create(1);conn_list[sockfd].fd = sockfd;
conn_list[sockfd].r_action.accept_callback = accept_cb;set_event(sockfd, EPOLLIN, 1);int set_event(int fd, int event, int flag){struct epoll_event ev;ev.data.fd = fd;ev.events = event;if(flag){epoll_ctl(epfd, EPOLL_CTL_ADD, fd, &ev);}else{epoll_ctl(epfd, EPOLL_CTL_MOD, fd, &ev);}}3.进入mainloop，根据事件类型调用相应的回调函数
while(1){struct epoll_event events[1024]={0};int nready = epoll_wait(epfd, events, 1024, -1);int i = 0;for(i = 0; i < nready; i++){int connfd = events[i].data.fd;printf("connfd:%d\n", connfd);//这个地方使用两个if而不是使用if-else if是因为该io可能同时存在EPOLLIN和EPOLLOUTif(events[i].events & EPOLLIN){conn_list[connfd].r_action.recv_callback(connfd);}if(events[i].events & EPOLLOUT){conn_list[connfd].send_callback(connfd);}}}3.1 三个回调函数
1.accept_cb:返回监听到的clientfd
int accept_cb(int fd){struct sockaddr_in clientaddr;int len = sizeof(clientaddr);memset(&clientaddr, 0, sizeof(clientaddr));int clientfd = accept(fd, (struct sockaddr*)&clientaddr, &len);if(clientfd < 0){printf("err clientf < 0");}event_register(clientfd, EPOLLIN);return clientfd;
}2.recv_cb:接收相应客户端发送的数据
int recv_cb(int fd){memset(conn_list[fd].rbuffer, 0, sizeof(conn_list[fd].rbuffer));int count = recv(fd, conn_list[fd].rbuffer, sizeof(conn_list[fd].rbuffer), 0);if(count == 0){printf("client disconnect: %d\n", fd);epoll_ctl(epfd, EPOLL_CTL_DEL, fd, NULL);close(fd);}else if(count < 0){printf("count:%d, errno:%s\n", count, strerror(errno));epoll_ctl(epfd, EPOLL_CTL_DEL, fd, NULL);close(fd);}memcpy(conn_list[fd].wbuffer, conn_list[fd].rbuffer, count);conn_list[fd].wbufferlength = count;printf("[%d]RECV: %s\n", count, conn_list[fd].rbuffer);set_event(fd, EPOLLOUT, 0);return count;
}3.send_cb:发送数据
int send_cb(int fd){int count = 0;if(conn_list[fd].wbufferlength > 0){count = send(fd, conn_list[fd].wbuffer, conn_list[fd].wbufferlength, 0);if(count <= 0) {printf("send failed: %s\n", strerror(errno));epoll_ctl(epfd, EPOLL_CTL_DEL, fd, NULL);close(fd);return -1;}conn_list[fd].wbufferlength = 0; // 清空发送缓冲区长度}set_event(fd, EPOLLIN, 0);return count;
}4.完整代码
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <unistd.h>
#include <netinet/in.h>
#include <string.h>
#include <sys/epoll.h>
#include <errno.h>#define BUFFERLENGTH 1024
#define CONNECTIONSIZE 1024typedef int (*CALLBACK)(int fd);int accept_cb(int fd);
int recv_cb(int fd);
int send_cb(int fd);int epfd = 0;struct conn{int fd;char rbuffer[BUFFERLENGTH];int rbufferlength;char wbuffer[BUFFERLENGTH];int wbufferlength;CALLBACK send_callback;union {CALLBACK accept_callback;CALLBACK recv_callback;}r_action;
};struct conn conn_list[CONNECTIONSIZE] = {0};int set_event(int fd, int event, int flag){struct epoll_event ev;ev.data.fd = fd;ev.events = event;if(flag){epoll_ctl(epfd, EPOLL_CTL_ADD, fd, &ev);}else{epoll_ctl(epfd, EPOLL_CTL_MOD, fd, &ev);}}int event_register(int fd, int event){ //将事件传入到conn_list中if(fd < 0){return -1;}conn_list[fd].fd = fd;conn_list[fd].r_action.accept_callback = recv_cb;conn_list[fd].send_callback = send_cb; memset(conn_list[fd].rbuffer, 0, BUFFERLENGTH);conn_list[fd].rbufferlength = 0;memset(conn_list[fd].wbuffer, 0, BUFFERLENGTH);conn_list[fd].wbufferlength = 0;set_event(fd, event, 1);
}int accept_cb(int fd){struct sockaddr_in clientaddr;int len = sizeof(clientaddr);memset(&clientaddr, 0, sizeof(clientaddr));int clientfd = accept(fd, (struct sockaddr*)&clientaddr, &len);if(clientfd < 0){printf("err clientf < 0");}event_register(clientfd, EPOLLIN);return clientfd;
}int recv_cb(int fd){memset(conn_list[fd].rbuffer, 0, sizeof(conn_list[fd].rbuffer));int count = recv(fd, conn_list[fd].rbuffer, sizeof(conn_list[fd].rbuffer), 0);if(count == 0){printf("client disconnect: %d\n", fd);epoll_ctl(epfd, EPOLL_CTL_DEL, fd, NULL);close(fd);}else if(count < 0){printf("count:%d, errno:%s\n", count, strerror(errno));epoll_ctl(epfd, EPOLL_CTL_DEL, fd, NULL);close(fd);}memcpy(conn_list[fd].wbuffer, conn_list[fd].rbuffer, count);conn_list[fd].wbufferlength = count;printf("[%d]RECV: %s\n", count, conn_list[fd].rbuffer);set_event(fd, EPOLLOUT, 0);return count;
}int send_cb(int fd){int count = 0;if(conn_list[fd].wbufferlength > 0){count = send(fd, conn_list[fd].wbuffer, conn_list[fd].wbufferlength, 0);if(count <= 0) {printf("send failed: %s\n", strerror(errno));epoll_ctl(epfd, EPOLL_CTL_DEL, fd, NULL);close(fd);return -1;}conn_list[fd].wbufferlength = 0; // 清空发送缓冲区长度}set_event(fd, EPOLLIN, 0);return count;
}int initserver(int port){int sockfd = socket(AF_INET, SOCK_STREAM, 0);struct sockaddr_in servaddr;memset(&servaddr, 0, sizeof(servaddr));servaddr.sin_family = AF_INET;servaddr.sin_addr.s_addr = htonl(INADDR_ANY);servaddr.sin_port = htons(port);if(-1 == bind(sockfd, (struct sockaddr*)&servaddr, sizeof(struct sockaddr))){perror("bind failed!");printf("bind failed!");}listen(sockfd, 10);return sockfd;}int main(){unsigned short port = 2077;int sockfd = initserver(port);epfd = epoll_create(1);conn_list[sockfd].fd = sockfd;conn_list[sockfd].r_action.accept_callback = accept_cb;set_event(sockfd, EPOLLIN, 1);while(1){struct epoll_event events[1024]={0};int nready = epoll_wait(epfd, events, 1024, -1);int i = 0;for(i = 0; i < nready; i++){int connfd = events[i].data.fd;printf("connfd:%d\n", connfd);//这个地方使用两个if而不是使用if-else if是因为该io可能同时存在EPOLLIN和EPOLLOUTif(events[i].events & EPOLLIN){conn_list[connfd].r_action.recv_callback(connfd);}if(events[i].events & EPOLLOUT){conn_list[connfd].send_callback(connfd);}}}
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