基于poll服务器的简单实现

涉及的点：

• poll函数

int poll(struct pollfd *fds, nfds_t nfds, int timeout);


	fds：要监听的文件描述符结构体数组
	    struct pollfd {
	        int fd; /* 文件描述符 */
	        short events; /* 监控的事件 */
	        short revents; /* 监控事件中满足条件返回的事件 */
	    };

    events：
         POLLIN         普通或带外优先数据可读,即POLLRDNORM | POLLRDBAND
         POLLOUT       	普通或带外数据可写
         POLLERR        发生错误
 
    nfds:           	监控数组中有多少文件描述符需要被监控（数组长度）
 
    timeout         毫秒级等待
        -1：阻塞等，#define INFTIM -1                Linux中没有定义此宏
        0：立即返回，不阻塞进程
        >0：等待指定毫秒数，如当前系统时间精度不够毫秒，向上取值

返回值：
参考select

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

#include "wrap.h"

#define MAXLINE 80
#define SERV_PORT 8000
#define OPEN_MAX 1024

int main(int argc, char *argv[])
{
    int i, j, maxi, listenfd, connfd, sockfd;
    int nready;                                 /*接收poll返回值, 记录满足监听事件的fd个数*/
    ssize_t n;

    char buf[MAXLINE], str[INET_ADDRSTRLEN];
    socklen_t clilen;
    struct pollfd client[OPEN_MAX];
    struct sockaddr_in cliaddr, servaddr;

    listenfd = Socket(AF_INET, SOCK_STREAM, 0);

    int opt = 1;
    setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));

    bzero(&servaddr, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr.sin_port = htons(SERV_PORT);

    Bind(listenfd, (struct sockaddr *)&servaddr, sizeof(servaddr));
    Listen(listenfd, 128);

    client[0].fd = listenfd;                    /* 要监听的第一个文件描述符 存入client[0]*/
    client[0].events = POLLIN;                  /* listenfd监听普通读事件 */

    for (i = 1; i < OPEN_MAX; i++)
        client[i].fd = -1;                      /* 用-1初始化client[]里剩下元素 0也是文件描述符,不能用 */

    maxi = 0;                                   /* client[]数组有效元素中最大元素下标 */

    for ( ; ; ) {
        nready = poll(client, maxi+1, -1);      /* 阻塞监听是否有客户端链接请求 */

        if (client[0].revents & POLLIN) {       /* listenfd有读事件就绪 */

            clilen = sizeof(cliaddr);
            connfd = Accept(listenfd, (struct sockaddr *)&cliaddr, &clilen);/* 接收客户端请求 Accept 不会阻塞 */
            printf("received from %s at PORT %d\n",
                    inet_ntop(AF_INET, &cliaddr.sin_addr, str, sizeof(str)),
                    ntohs(cliaddr.sin_port));

            for (i = 1; i < OPEN_MAX; i++)
                if (client[i].fd < 0) {
                    client[i].fd = connfd;      /* 找到client[]中空闲的位置,存放accept返回的connfd */
                    break;
                }

            if (i == OPEN_MAX)                  /* 达到了最大客户端数 */
                perr_exit("too many clients");

            client[i].events = POLLIN;          /* 设置刚刚返回的connfd,监控读事件 */
            if (i > maxi)
                maxi = i;                       /* 更新client[]中最大元素下标 */
            if (--nready <= 0)
                continue;                       /* 没有更多就绪事件时,继续回到poll阻塞 */
        }

        for (i = 1; i <= maxi; i++) {           /* 前面的if没满足,说明没有listenfd满足. 检测client[] 看是那个connfd就绪 */
            if ((sockfd = client[i].fd) < 0)
                continue;

            if (client[i].revents & POLLIN) {

                if ((n = Read(sockfd, buf, MAXLINE)) < 0) {
                    /* connection reset by client */
                    if (errno == ECONNRESET) {  /* 收到RST标志 */
                        printf("client[%d] aborted connection\n", i);
                        Close(sockfd);
                        client[i].fd = -1;      /* poll中不监控该文件描述符,直接置为-1即可,不用像select中那样移除 */
                    } else
                        perr_exit("read error");

                } else if (n == 0) {            /* 说明客户端先关闭链接 */
                    printf("client[%d] closed connection\n", i);
                    Close(sockfd);
                    client[i].fd = -1;
                } else {
                    for (j = 0; j < n; j++)
                        buf[j] = toupper(buf[j]);
                    Writen(sockfd, buf, n);
                }
                if (--nready <= 0)
                    break;
            }
        }
    }
    return 0;
}

c++版

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

#include 
#include 
#include 
#include 

#include 
#include 

#define ERR_EXIT(m) \
        do \
        { \
                perror(m); \
                exit(EXIT_FAILURE); \
        } while(0)

typedef std::vector<struct pollfd> PollFdList;

int main(void)
{
	signal(SIGPIPE, SIG_IGN);
	signal(SIGCHLD, SIG_IGN);

	//int idlefd = open("/dev/null", O_RDONLY | O_CLOEXEC);
	int listenfd;

	//非阻塞socket
	if ((listenfd = socket(PF_INET, SOCK_STREAM | SOCK_NONBLOCK | SOCK_CLOEXEC, IPPROTO_TCP)) < 0)
		ERR_EXIT("socket");

	struct sockaddr_in servaddr;
	memset(&servaddr, 0, sizeof(servaddr));
	servaddr.sin_family = AF_INET;
	servaddr.sin_port = htons(5188);
	servaddr.sin_addr.s_addr = htonl(INADDR_ANY);

	int on = 1;
	if (setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
		ERR_EXIT("setsockopt");

	if (bind(listenfd, (struct sockaddr*)&servaddr, sizeof(servaddr)) < 0)
		ERR_EXIT("bind");
	if (listen(listenfd, SOMAXCONN) < 0)
		ERR_EXIT("listen");

	struct pollfd pfd;
	pfd.fd = listenfd;
	pfd.events = POLLIN;

	PollFdList pollfds;
	pollfds.push_back(pfd);

	int nready;

	struct sockaddr_in peeraddr;
	socklen_t peerlen;
	int connfd;

	while (1)
	{
		//&*pollfds.begin() ==> 结构体首地址  （c++11：pollfds.data()）
		nready = poll(&*pollfds.begin(), pollfds.size(), -1);
		if (nready == -1)
		{
			if (errno == EINTR)
				continue;
			
			ERR_EXIT("poll");
		}
		if (nready == 0)	// nothing happended
			continue;
		
		if (pollfds[0].revents & POLLIN)
		{
			peerlen = sizeof(peeraddr);
			connfd = accept4(listenfd, (struct sockaddr*)&peeraddr,
						&peerlen, SOCK_NONBLOCK | SOCK_CLOEXEC);

			if (connfd == -1)
				ERR_EXIT("accept4");

/*
			if (connfd == -1)
			{
				if (errno == EMFILE)
				{
					close(idlefd);
					idlefd = accept(listenfd, NULL, NULL);
					close(idlefd);
					idlefd = open("/dev/null", O_RDONLY | O_CLOEXEC);
					continue;
				}
				else
					ERR_EXIT("accept4");
			}
*/

			pfd.fd = connfd;
			pfd.events = POLLIN;
			pfd.revents = 0;
			pollfds.push_back(pfd);
			--nready;

			// ���ӳɹ�
			std::cout<<"ip="<<inet_ntoa(peeraddr.sin_addr)<<
				" port="<<ntohs(peeraddr.sin_port)<<std::endl;
			if (nready == 0)
				continue;
		}

		for (PollFdList::iterator it=pollfds.begin()+1;
			it != pollfds.end() && nready >0; ++it)
		{
				if (it->revents & POLLIN)
				{
					--nready;
					connfd = it->fd;
					char buf[1024] = {0};
					int ret = read(connfd, buf, 1024);
					if (ret == -1)
						ERR_EXIT("read");
					if (ret == 0)
					{
						std::cout<<"client close"<<std::endl;
						it = pollfds.erase(it);
						--it;

						close(connfd);
						continue;
					}

					std::cout<<buf;
					write(connfd, buf, strlen(buf));
					
				}
		}
	}

	return 0;
}