服务器之poll

poll服务器方法采用将监听端口用数组存放起来，这样就不需要轮询的监听整个文件描述符了

#include <poll.h>
int poll(struct pollfd *fds, nfds_t nfds, int timeout);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 */};POLLIN            普通或带外优先数据可读,即POLLRDNORM | POLLRDBANDPOLLRDNORM        数据可读POLLRDBAND        优先级带数据可读POLLPRI         高优先级可读数据POLLOUT        普通或带外数据可写POLLWRNORM        数据可写POLLWRBAND        优先级带数据可写POLLERR         发生错误POLLHUP         发生挂起POLLNVAL         描述字不是一个打开的文件nfds             监控数组中有多少文件描述符需要被监控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

如果不再监控某个文件描述符时，可以把pollfd中，fd设置为-1，poll不再监控此pollfd，下次返回时，把revents设置为0。

/* server.c */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <poll.h>
#include <errno.h>
#include "wrap.h"#define MAXLINE 80
#define SERV_PORT 6666
#define OPEN_MAX 1024int main(int argc, char *argv[])
{int i, j, maxi, listenfd, connfd, sockfd;int nready;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);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, 20);client[0].fd = listenfd;client[0].events = POLLRDNORM;                     /* 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 */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 */if (client[0].revents & POLLRDNORM) {         /* 有客户端链接请求 */clilen = sizeof(cliaddr);connfd = Accept(listenfd, (struct sockaddr *)&cliaddr, &clilen);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)perr_exit("too many clients");client[i].events = POLLRDNORM;         /* 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++) {             /* 检测client[] */if ((sockfd = client[i].fd) < 0)continue;if (client[i].revents & (POLLRDNORM | POLLERR)) {if ((n = Read(sockfd, buf, MAXLINE)) < 0) {if (errno == ECONNRESET) { /* 当收到 RST标志时 *//* connection reset by client */printf("client[%d] aborted connection\n", i);Close(sockfd);client[i].fd = -1;} else {perr_exit("read error");}} else if (n == 0) {/* connection closed by client */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;                 /* no more readable descriptors */}}}return 0;
}

client

/* client.c */
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <netinet/in.h>
#include "wrap.h"#define MAXLINE 80
#define SERV_PORT 6666int main(int argc, char *argv[])
{struct sockaddr_in servaddr;char buf[MAXLINE];int sockfd, n;sockfd = Socket(AF_INET, SOCK_STREAM, 0);bzero(&servaddr, sizeof(servaddr));servaddr.sin_family = AF_INET;inet_pton(AF_INET, "127.0.0.1", &servaddr.sin_addr);servaddr.sin_port = htons(SERV_PORT);Connect(sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr));while (fgets(buf, MAXLINE, stdin) != NULL) {Write(sockfd, buf, strlen(buf));n = Read(sockfd, buf, MAXLINE);if (n == 0)printf("the other side has been closed.\n");elseWrite(STDOUT_FILENO, buf, n);}Close(sockfd);return 0;
}