IO多路复用（二） -- select、poll、epoll实现TCP反射程序

接着上文IO多路复用（一）-- Select、Poll、Epoll，接下来将演示一个TCP回射程序，源代码来自于该博文https://www.cnblogs.com/Anker/p/3258674.html 博主的几篇相关的文章，在这里将其进行了整合，突出select、poll和epoll不同方法之间的比较，但是代码的结构相同，为了突出方法之间的差别，可能有的代码改动的并不合理，实际中使用并非这么写。

程序逻辑

该程序的主要逻辑如下：

服务器：
	1. 开启服务器套接字
	2. 将服务器套接字加入要监听的集合中（select的fd_set、poll的pollfd、epoll调用epoll_ctl）
	3. 进入循环，调用IO多路复用的API函数（select/poll/epoll_create），如果有事件产生：
		3.1. 服务器套接字产生的事件，添加新的客户端到监听集合中
		3.2. 客户端套接字产生的事件，读取数据，并立马回传给客户端

客户端：
	1. 开启客户端套接字
	2. 将客户端套接字和标准输入文件描述符加入要监听的集合中（select的fd_set、poll的pollfd、epoll调用epoll_ctl）
	3. 进入循环，调用IO多路复用的API函数（select/poll/epoll_create），如果有事件产生：
		3.1. 客户端套接字产生的事件，则读取数据，将其输出到控制台
		3.2. 标准输入文件描述符产生的事件，则读取数据，将其通过客户端套接字传给服务器

multiplexing.h

具体代码如下，首先是头文件

//multiplexing.h

#ifndef MULTIPLEXING_H
#define MULTIPLEXING_H

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <poll.h>
#include <unistd.h>
#include <sys/types.h>
#include <arpa/inet.h>
#include <sys/select.h>
#include <sys/epoll.h>
#include <unistd.h>
using namespace std;

#define MAXLINE     1024
class Multiplexing {
protected:
	static const int DEFAULT_IO_MAX = 10; //默认的最大文件描述符
	static const int INFTIM = -1;
	int io_max; //记录最大文件描述符
	int listenfd; //监听句柄
public:
	Multiplexing() { this->io_max = DEFAULT_IO_MAX; }
	Multiplexing(int max, int listenfd) { this->io_max = max; this->listenfd = listenfd; }
	~Multiplexing() {}

	virtual void server_do_multiplexing() = 0; //服务端io多路复用
	virtual void client_do_multiplexing() = 0; //客户端io多路复用
	virtual void handle_client_msg() = 0; //处理客户端消息
	virtual bool accept_client_proc() = 0; //接收客户端连接
	virtual bool add_event(int confd, int event) = 0;
	virtual int wait_event() = 0; // 等待事件
};

//-----------------select-------------------------
class MySelect : public Multiplexing {
private:
	fd_set* allfds;      //句柄集合
	int* clifds;   //客户端集合
	int maxfd; //记录句柄的最大值
	int cli_cnt; //客户端个数

public:
	MySelect() : Multiplexing() { allfds = NULL; clifds = NULL; maxfd = 0; cli_cnt = 0; }
	MySelect(int max, int listenfd);
	~MySelect() {
		if (allfds) {
			delete allfds;
			allfds = NULL;
		}
		if (clifds) {
			delete clifds;
			clifds = NULL;
		}
	}

	void server_do_multiplexing();
	void client_do_multiplexing();
	void handle_client_msg();
	bool accept_client_proc();
	bool add_event(int confd, int event);
	bool init_event(); //每次调用select前都要重新设置文件描述符
	int wait_event(); // 等待事件

};

//-----------------poll-------------------------
typedef struct pollfd Pollfd;
class MyPoll : public Multiplexing {
private:
	Pollfd* clientfds; //poll中使用pollfd结构体指定一个被监视的文件描述符
	int max_index; //记录当前clientfds数组中使用的最大下标

public:
	MyPoll() : Multiplexing() { clientfds = NULL; max_index = -1; }
	MyPoll(int max, int listenfd);
	~MyPoll() {
		if (clientfds) {
			delete clientfds;
			clientfds = NULL;
		}
	}

	void server_do_multiplexing();
	void client_do_multiplexing();
	void handle_client_msg();
	bool accept_client_proc();
	bool add_event(int confd, int event);
	int wait_event(); // 等待事件
};

//-----------------epoll-------------------------
typedef struct epoll_event Epoll_event;
class MyEpoll : public Multiplexing {
private:
	int epollfd; //epoll的句柄，用来管理多个文件描述符
	Epoll_event *events; //事件数组
	int nready; //在handle_client_msg函数中用到，传给handle_client_msg函数的当前事件的个数
public:
	MyEpoll() : Multiplexing() { events = NULL; epollfd = -1; }
	MyEpoll(int max, int listenfd);
	~MyEpoll() {
		if (events) {
			delete events;
			events = NULL;
		}
	}

	void server_do_multiplexing();
	void client_do_multiplexing();
	void handle_client_msg();
	bool accept_client_proc();
	bool add_event(int confd, int event);
	bool delete_event(int confd, int event);
	int wait_event(); // 等待事件
};

#endif // !MULTIPLEXING_H

multiplexing.cpp

然后是函数的实现，从各个函数的实现可以看到select、poll、epoll在使用过程中的区别，具体看代码注释

//multiplexing.cpp

#include "multiplexing.h"

//--------------------------select------------------
MySelect::MySelect(int max, int listenfd) : Multiplexing(max, listenfd) {
	this->allfds = new fd_set[this->io_max];
	this->clifds = new int[this->io_max];
	if (NULL == this->allfds || NULL == this->clifds) {
		perror("initialization failed!");
		exit(-1);
	}
	this->cli_cnt = 0;
	this->maxfd = 0;

	//初始化客户连接描述符
	int i;
	for (i = 0; i < io_max; i++) {
		this->clifds[i] = -1;
	}
}

void MySelect::server_do_multiplexing() {
	int  nready = 0;
	int i = 0;

	while (1) {
		//重新初始化fd_set集合 -- 这里与poll不同
		init_event();

		/*开始轮询接收处理服务端和客户端套接字*/
		nready = wait_event();
		if (-1 == nready) return;
		if (0 == nready) continue;

		if (FD_ISSET(this->listenfd, this->allfds)) {
			/*监听客户端请求*/
			if (!accept_client_proc())  //处理连接请求
				continue;
			if (--nready <= 0) //说明此时产生的事件个数小于等于1，所以不必再处理下面的客户连接信息
				continue;
		}

		/*接受处理客户端消息*/
		handle_client_msg();
	}
}

void MySelect::client_do_multiplexing() {
	char sendline[MAXLINE], recvline[MAXLINE];
	int n;
	this->maxfd = -1;
	int nready = -1;
	if (this->io_max < 2) {
		perror("please increase the max number of io!");
		exit(1);
	}

	//添加连接描述符
	if (!add_event(this->listenfd, -1)) {
		perror("add event error!");
		exit(1);
	}

	//添加标准输入描述符
	if (!add_event(STDIN_FILENO, -1)) {
		perror("add event error!");
		exit(1);
	}

	while (1) {
		//重新初始化fd_set集合 -- 这里与poll不同
		init_event();

		//等待事件产生
		nready = wait_event();
		if (-1 == nready) return;
		if (0 == nready) continue;

		//是否有客户信息准备好
		if (FD_ISSET(this->listenfd, this->allfds)) {
			n = read(this->listenfd, recvline, MAXLINE);
			if (n <= 0) {
				fprintf(stderr, "client: server is closed.\n");
				close(this->listenfd);
				return;
			}
			write(STDOUT_FILENO, recvline, n);
		}
		//测试标准输入是否准备好
		if (FD_ISSET(STDIN_FILENO, this->allfds)) {
			n = read(STDIN_FILENO, sendline, MAXLINE);
			if (n <= 0) {
				shutdown(this->listenfd, SHUT_WR);
				continue;
			}
			write(this->listenfd, sendline, n);
		}
	}
}

bool MySelect::init_event() {
	FD_ZERO(this->allfds); //重新设置文件描述符

						   /*添加监听套接字*/
	FD_SET(this->listenfd, this->allfds);
	this->maxfd = this->listenfd;

	int i;
	int  clifd = -1;
	/*添加客户端套接字*/
	for (i = 0; i < this->cli_cnt; i++) {
		clifd = this->clifds[i];
		/*去除无效的客户端句柄*/
		if (clifd != -1) {
			FD_SET(clifd, this->allfds);
		}
		this->maxfd = (clifd > this->maxfd ? clifd : this->maxfd);
	}
}

bool MySelect::accept_client_proc() {
	struct sockaddr_in cliaddr;
	socklen_t cliaddrlen;
	cliaddrlen = sizeof(cliaddr);
	int connfd;

	//接受新的连接
	if ((connfd = accept(this->listenfd,
                         (struct sockaddr*)&cliaddr, &cliaddrlen)) == -1) {
		if (errno == EINTR)
			return false;
		else {
			perror("accept error:");
			exit(1);
		}
	}
	fprintf(stdout, "accept a new client: %s:%d\n",
            inet_ntoa(cliaddr.sin_addr), cliaddr.sin_port);
	return add_event(connfd, -1); //添加新的描述符
}

bool MySelect::add_event(int connfd, int event) { //在select中event并没有作用
												  //将新的连接描述符添加到数组中
	int i = 0;
	for (i = 0; i < io_max; i++) {
		if (this->clifds[i] < 0) {
			this->clifds[i] = connfd;
			this->cli_cnt++;
			break;
		}
	}

	if (i == io_max) {
		fprintf(stderr, "too many clients.\n");
		return false;
	}

	//将新的描述符添加到读描述符集合中
	FD_SET(connfd, this->allfds);
	if (connfd > this->maxfd) this->maxfd = connfd;
	return true;
}

void MySelect::handle_client_msg() {
	int i = 0, n = 0;
	int clifd;
	char buf[MAXLINE];
	memset(buf, 0, MAXLINE);

	//处理信息
	for (i = 0; i <= this->cli_cnt; i++) {
		clifd = this->clifds[i];
		if (clifd < 0) {
			continue;
		}

		/*判断客户端套接字是否有数据*/
		if (FD_ISSET(clifd, this->allfds)) {
			//接收客户端发送的信息
			n = read(clifd, buf, MAXLINE);

			if (n <= 0) {
				/*n==0表示读取完成，客户都关闭套接字*/
				FD_CLR(clifd, this->allfds);
				close(clifd);
				this->clifds[i] = -1;
				continue;
			}

			//回写数据
			printf("recv buf is :%s\n", buf);
			write(clifd, buf, n);
			return;
		}
	}
}

int MySelect::wait_event() {
	struct timeval tv;

	/*每次调用select前都要重新设置文件描述符和时间，因为事件发生后，文件描述符和时间都被内核修改啦*/
	tv.tv_sec = 30;
	tv.tv_usec = 0;

	/*开始轮询接收处理服务端和客户端套接字*/
	int nready = select(this->maxfd + 1, this->allfds, NULL, NULL, &tv);
	if (nready == -1) {
		fprintf(stderr, "select error:%s.\n", strerror(errno));
	}
	if (nready == 0) {
		fprintf(stdout, "select is timeout.\n");
	}
	return nready;
}

//-----------------poll-------------------------
MyPoll::MyPoll(int max, int listenfd) : Multiplexing(max, listenfd) {
	this->clientfds = new Pollfd[this->io_max];
	//初始化客户连接描述符
	int i;
	for (i = 0; i < io_max; i++) {
		this->clientfds[i].fd = -1;
	}
	this->max_index = -1;
}

void MyPoll::server_do_multiplexing() {
	int sockfd;
	int i;
	int nready;
	this->max_index = -1;

	//注意：需要将监听描述符添加在第一个位置
	if (!add_event(this->listenfd, POLLIN)) {
		perror("add listen event error!");
		return;
	}

	//循环处理
	while (1) {
		//等待事件，获取可用描述符的个数
		nready = wait_event();
		if (nready == -1) {
			return;
		}
		if (nready == 0) {
			continue;
		}

		//测试监听描述符是否准备好
		if (this->clientfds[0].revents & POLLIN) {
			if (!accept_client_proc())  //处理连接请求
				continue;
			if (--nready <= 0) //说明此时产生的事件个数小于等于1，所以不必再处理下面的客户连接信息
				continue;
		}

		//处理客户连接
		handle_client_msg();
	}
}

void MyPoll::client_do_multiplexing() {
	char    sendline[MAXLINE], recvline[MAXLINE];
	int n;
	this->max_index = -1;
	int nready = -1;
	if (this->io_max < 2) {
		perror("please increase the max number of io!");
		exit(1);
	}

	//添加连接描述符
	if (!add_event(this->listenfd, POLLIN)) {
		perror("add event error!");
		exit(1);
	}

	//添加标准输入描述符
	if (!add_event(STDIN_FILENO, POLLIN)) {
		perror("add event error!");
		exit(1);
	}

	while (1) {
		//等待事件产生
		nready = wait_event();
		if (-1 == nready) return;
		if (0 == nready) continue;

		//是否有客户信息准备好
		if (this->clientfds[0].revents & POLLIN) {
			n = read(this->listenfd, recvline, MAXLINE);
			if (n <= 0) {
				fprintf(stderr, "client: server is closed.\n");
				close(this->listenfd);
				return;
			}
			write(STDOUT_FILENO, recvline, n);
		}
		//测试标准输入是否准备好
		if (this->clientfds[1].revents & POLLIN) {
			n = read(STDIN_FILENO, sendline, MAXLINE);
			if (n <= 0) {
				shutdown(this->listenfd, SHUT_WR);
				continue;
			}
			write(this->listenfd, sendline, n);
		}
	}
}

bool MyPoll::accept_client_proc() {
	struct sockaddr_in cliaddr;
	socklen_t cliaddrlen;
	cliaddrlen = sizeof(cliaddr);
	int connfd;

	//接受新的连接
	if ((connfd = accept(this->listenfd,
                         (struct sockaddr*)&cliaddr, &cliaddrlen)) == -1) {
		if (errno == EINTR)
			return false;
		else {
			perror("accept error:");
			exit(1);
		}
	}
	fprintf(stdout, "accept a new client: %s:%d\n",
            inet_ntoa(cliaddr.sin_addr), cliaddr.sin_port);
	return add_event(connfd, POLLIN); //添加新的描述符
}

bool MyPoll::add_event(int connfd, int event) {
	//将新的连接描述符添加到数组中
	int i;
	for (i = 0; i < io_max; i++) {
		if (this->clientfds[i].fd < 0) {
			this->clientfds[i].fd = connfd;
			break;
		}
	}

	if (i == io_max) {
		fprintf(stderr, "too many clients.\n");
		return false;
	}

	//将新的描述符添加到读描述符集合中
	this->clientfds[i].events = event;
	if (i > this->max_index) this->max_index = i;
	return true;
}

void MyPoll::handle_client_msg() {
	int i, n;
	char buf[MAXLINE];
	memset(buf, 0, MAXLINE);

	//处理信息
	for (i = 1; i <= this->max_index; i++) {
		if (this->clientfds[i].fd < 0)
			continue;

		//测试客户描述符是否准备好
		if (this->clientfds[i].revents & POLLIN) {
			//接收客户端发送的信息
			n = read(this->clientfds[i].fd, buf, MAXLINE);
			if (n <= 0) {
				close(this->clientfds[i].fd);
				this->clientfds[i].fd = -1;
				continue;
			}

			write(STDOUT_FILENO, buf, n);
			//向客户端发送buf
			write(this->clientfds[i].fd, buf, n);
		}
	}
}

int MyPoll::wait_event() {
	/*开始轮询接收处理服务端和客户端套接字*/
	int nready = nready = poll(this->clientfds, this->max_index + 1, INFTIM);
	if (nready == -1) {
		fprintf(stderr, "poll error:%s.\n", strerror(errno));
	}
	if (nready == 0) {
		fprintf(stdout, "poll is timeout.\n");
	}
	return nready;
}

//------------------------epoll---------------------------
MyEpoll::MyEpoll(int max, int listenfd) : Multiplexing(max, listenfd) {
	this->events = new Epoll_event[this->io_max];
	//创建一个描述符
	this->epollfd = epoll_create(this->io_max);
}

void MyEpoll::server_do_multiplexing() {
	int i, fd;
	int nready;
	char buf[MAXLINE];
	memset(buf, 0, MAXLINE);

	//添加监听描述符事件
	if (!add_event(this->listenfd, EPOLLIN)) {
		perror("add event error!");
		exit(1);
	}
	while (1) {
		//获取已经准备好的描述符事件
		nready = wait_event();
		this->nready = nready;
		if (-1 == nready) return;
		if (0 == nready) continue;

		//进行遍历
		/**这里和poll、select都不同，因为并不能直接判断监听的事件是否产生，
		所以需要一个for循环遍历，这个for循环+判断类似于poll中
		if (FD_ISSET(this->listenfd, this->allfds))、
		select中的if (this->clientfds[0].revents & POLLIN)
		这里只是尽量写的跟poll、select中的结构类似，
		但是实际代码中，不应该这么写，这么写多加了一个for循环**/
		for (i = 0; i < nready; i++) {
			fd = events[i].data.fd;
			//根据描述符的类型和事件类型进行处理
			if ((fd == this->listenfd) && (events[i].events & EPOLLIN)) {  //监听事件
				/*监听客户端请求*/
				if (!accept_client_proc())  //处理连接请求
					continue;
                //说明此时产生的事件个数小于等于1，所以不必再处理下面的客户连接信息
				if (--nready <= 0)
					continue;
			}
		}

		//处理客户端事件
		handle_client_msg();
	}
	close(epollfd);
}

bool MyEpoll::accept_client_proc() {
	struct sockaddr_in cliaddr;
	socklen_t cliaddrlen;
	cliaddrlen = sizeof(cliaddr);
	int connfd;

	//接受新的连接
	if ((connfd = accept(this->listenfd,
                         (struct sockaddr*)&cliaddr, &cliaddrlen)) == -1) {
		if (errno == EINTR)
			return false;
		else {
			perror("accept error:");
			exit(1);
		}
	}
	fprintf(stdout, "accept a new client: %s:%d\n",
            inet_ntoa(cliaddr.sin_addr), cliaddr.sin_port);
	return add_event(connfd, EPOLLIN); //添加新的描述符
}

void MyEpoll::client_do_multiplexing() {
	char    sendline[MAXLINE], recvline[MAXLINE];
	int n;
	int nready = -1;
	int i, fd;
	if (this->io_max < 2) {
		perror("please increase the max number of io!");
		exit(1);
	}

	//添加连接描述符
	if (!add_event(this->listenfd, POLLIN)) {
		perror("add event error!");
		exit(1);
	}

	//添加标准输入描述符
	if (!add_event(STDIN_FILENO, POLLIN)) {
		perror("add event error!");
		exit(1);
	}

	while (1) {
		//等待事件产生
		nready = wait_event();
		if (-1 == nready) return;
		if (0 == nready) continue;

		for (i = 0; i < nready; i++) {
			fd = events[i].data.fd;
			//根据描述符的类型和事件类型进行处理
			if ((fd == this->listenfd) && (events[i].events & EPOLLIN)) {  //监听事件
				n = read(this->listenfd, recvline, MAXLINE);
				if (n <= 0) {
					fprintf(stderr, "client: server is closed.\n");
					close(this->listenfd);
					return;
				}
				write(STDOUT_FILENO, recvline, n);
			}
			else {
				n = read(STDIN_FILENO, sendline, MAXLINE);
				if (n <= 0) {
					shutdown(this->listenfd, SHUT_WR);
					continue;
				}
				write(this->listenfd, sendline, n);
			}
		}
	}
}

bool MyEpoll::add_event(int connfd, int event) {
	//将新的描述符添加到读描述符集合中
	Epoll_event ev;
	ev.events = event;
	ev.data.fd = connfd;
	return epoll_ctl(this->epollfd, EPOLL_CTL_ADD, connfd, &ev) == 0;
}

void MyEpoll::handle_client_msg() {
	int i, fd;
	char buf[MAXLINE];
	memset(buf, 0, MAXLINE);

	//处理信息
	for (i = 0; i <= this->nready; i++) {
		fd = this->events[i].data.fd;
		if (fd == this->listenfd)
			continue;

		if (events[i].events & EPOLLIN) {
			int n = read(fd, buf, MAXLINE);
			if (n <= 0) {
				perror("read error:");
				close(fd);
				delete_event(fd, EPOLLIN);
			}
			else {
				write(STDOUT_FILENO, buf, n);
				//向客户端发送buf
				write(fd, buf, strlen(buf));
			}
		}
	}
}

int MyEpoll::wait_event() {
	/*开始轮询接收处理服务端和客户端套接字*/
	int nready = epoll_wait(this->epollfd, this->events, this->io_max, INFTIM);;
	if (nready == -1) {
		fprintf(stderr, "poll error:%s.\n", strerror(errno));
	}
	if (nready == 0) {
		fprintf(stdout, "poll is timeout.\n");
	}
	return nready;
}

bool MyEpoll::delete_event(int fd, int state) {
	Epoll_event ev;
	ev.events = state;
	ev.data.fd = fd;
	return epoll_ctl(this->epollfd, EPOLL_CTL_DEL, fd, &ev) == 0;
}

服务器代码

#include "multiplexing.h"

#define IPADDRESS   "127.0.0.1"
#define PORT        8787
#define LISTENQ     5
#define OPEN_MAX    1000

//函数声明
//创建套接字并进行绑定
static int socket_bind(const char* ip, int port);

int main(int argc, char *argv[]) {
	int listenfd = socket_bind(IPADDRESS, PORT);
	if (listenfd < 0) {
		perror("socket bind error");
		return 0;
	}

	listen(listenfd, LISTENQ);

    // 改动此处，调用不同的IO复用函数
	MySelect mltp(OPEN_MAX, listenfd);
    //MyPoll mltp(OPEN_MAX, listenfd);
    //MyEpoll mltp(OPEN_MAX, listenfd);

	mltp.server_do_multiplexing(); //处理服务端
	return 0;
}

static int socket_bind(const char* ip, int port) {
	int  listenfd;
	struct sockaddr_in servaddr;
	listenfd = socket(AF_INET, SOCK_STREAM, 0);
	if (listenfd == -1) {
		perror("socket error:");
		exit(1);
	}
	bzero(&servaddr, sizeof(servaddr));
	servaddr.sin_family = AF_INET;
	inet_pton(AF_INET, ip, &servaddr.sin_addr);
	servaddr.sin_port = htons(port);
	if (bind(listenfd, (struct sockaddr*)&servaddr, sizeof(servaddr)) == -1) {
		perror("bind error: ");
		exit(1);
	}
	return listenfd;
}

客户端代码

#include "multiplexing.h"
#define MAXLINE     1024
#define IPADDRESS   "127.0.0.1"
#define SERV_PORT   8787

static void handle_connection(int sockfd);

int main(int argc, char *argv[]) {
	int                 sockfd;
	struct sockaddr_in  servaddr;
	sockfd = socket(AF_INET, SOCK_STREAM, 0);
	bzero(&servaddr, sizeof(servaddr));
	servaddr.sin_family = AF_INET;
	servaddr.sin_port = htons(SERV_PORT);
	inet_pton(AF_INET, IPADDRESS, &servaddr.sin_addr);
	connect(sockfd, (struct sockaddr*)&servaddr, sizeof(servaddr));

    // 改动此处，调用不同的IO复用函数
	MySelect mltp(2, sockfd);
    //MyPoll mltp(2, sockfd);
    //MyEpoll mltp(2, sockfd);

	poll.client_do_multiplexing(); // 处理客户端
	return 0;
}

运行结果

服务端：

客户端：

完整代码可以访问笔者github：https://github.com/yearsj/ClientServerProject.git

参考资料

IO多路复用之select总结

IO多路复用之poll总结

IO多路复用之epoll总结

作者：yearsj

转载请注明出处：https://www.cnblogs.com/yearsj/p/9647351.html

segmentfault对应博文：https://segmentfault.com/a/1190000016400430