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
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
