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IO多路复用通常用于处理单进程高并发，在Linux中，一切皆文件，一个socket连接会对应一个文件描述符，在监听多个文件描述符的状态应用中epoll相对于select和poll效率更高
epoll本质是系统在内核维护了一颗红黑树，监听的文件描述符会作为新的节点插入红黑树，epoll会等待有状态变化的节点记录在链表里，然后拷贝到用户所给的数组里面返回出来
以下是一个独立的服务端代码，可以补充业务代码进行具体使用
sever.h
//
// Created by YEZI on 2024/5/24.
//#ifndef SEVER_H
#define SEVER_H
#include <iostream>
#include <cstdlib>
#include <unistd.h>
#include <sys/epoll.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sstream>
#define MAX_EVENTS 8
#define PORT 8888
#define BUFFER_SIZE 512
#define BACKLOG_SIZE 16 // 请求队列最大长度class Sever {
private:uint16_t port;int server_fd = -1;int epoll_fd = -1;sockaddr_in server_addr{}, client_addr{};socklen_t client_addr_len = sizeof(client_addr);epoll_event event{}, events[MAX_EVENTS]{};public:explicit Sever(uint16_t port = PORT): port(port) {// 创建套接字// AF_INET : 表示使用 IPv4 地址 可选参数// SOCK_STREAM 表示使用面向连接的数据传输方式，// IPPROTO_TCP 表示使用 TCP 协议server_fd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);if (server_fd == -1) {std::cerr << "Failed to create socket\n";exit(EXIT_FAILURE);}// 设置服务器地址server_addr.sin_family = AF_INET; // IPv4server_addr.sin_addr.s_addr = INADDR_ANY; // INADDR_ANY：0.0.0.0 表示本机所有IP地址server_addr.sin_port = htons(PORT);// 绑定套接字if (bind(server_fd, (sockaddr *) &server_addr, sizeof(server_addr)) == -1) {std::cerr << "Failed to bind socket\n";exit(EXIT_FAILURE);}// 监听套接字if (listen(server_fd, BACKLOG_SIZE) == -1) {std::cerr << "Failed to listen on socket\n";exit(EXIT_FAILURE);}// 创建 epoll 实例epoll_fd = epoll_create1(0); // flag设置为0同epoll_create()if (epoll_fd == -1) {std::cerr << "Failed to create epoll instance\n";exit(EXIT_FAILURE);}// 将服务器套接字添加到 epoll 实例中event.events = EPOLLIN | EPOLLET; // 监听事件类型 EPOLLIN表示有数据可读 EPOLLET表示边缘触发仅在状态变化时通知event.data.fd = server_fd;if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, server_fd, &event) == -1) {std::cerr << "Failed to add server socket to epoll\n";exit(EXIT_FAILURE);}std::cout << "Server started. Listening on port " << PORT << "...\n";}void run() {while (true) {// 使用 epoll 等待事件 参数timeout为等待时间，-1等死int num_ready = epoll_wait(epoll_fd, events, MAX_EVENTS, -1);if (num_ready == -1) {std::cerr << "Error in epoll_wait\n";exit(EXIT_FAILURE);}for (int i = 0; i < num_ready; ++i) {if (events[i].data.fd == server_fd) {// 有新的连接请求int client_fd = accept(server_fd, (sockaddr *) &client_addr, &client_addr_len);if (client_fd == -1) {std::cerr << "Failed to accept client connection\n";continue;}std::cout << "New connection from " << inet_ntoa(client_addr.sin_addr)<< ":" << ntohs(client_addr.sin_port) << std::endl;// 将新的客户端套接字添加到 epoll 实例中event.events = EPOLLIN | EPOLLET;event.data.fd = client_fd;if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, client_fd, &event) == -1) {std::cerr << "Failed to add client socket to epoll\n";exit(EXIT_FAILURE);}} else {// 有数据到达现有客户端套接字char buffer[BUFFER_SIZE]{};ssize_t bytes_received = recv(events[i].data.fd, buffer, BUFFER_SIZE, 0);if (bytes_received <= 0) {if (bytes_received == 0) {// 客户端关闭连接std::cout << "Client disconnected\n";} else {std::cerr << "Error in recv\n";}// 关闭客户端套接字，并从 epoll 实例中移除close(events[i].data.fd);epoll_ctl(epoll_fd, EPOLL_CTL_DEL, events[i].data.fd, nullptr);} else {// 接收到数据，原样发送回客户端，此处为业务代码补充处send(events[i].data.fd, buffer, bytes_received, 0);std::istringstream iss(buffer);std::string data;while (iss >> data) {std::cout << data << ' ';}std::cout<<std::endl;}}}}}~Sever() {// 关闭服务器套接字和 epoll 实例close(server_fd);close(epoll_fd);}
};
#endif //SEVER_H
main.cpp
#include"sever.h"
int main() {Sever sever;sever.run();
}
简单测试服务端，打开Linux终端，用一下命令连接服务器后即可传输数据
telnet localhost 8888