网络编程学习笔记(poll函数)

其原型为：

#include <poll.h>
int poll(struct pollfd *fdarray, unsigned long nfds, int timeout);

成功时返回准备好描述字的个数，超时返回0,出错返回 -1

第一个参数是指向一个结构数组第一个元素的指针，每个数组元素都是一个pollfd结构

结构体定义如下：

struct pollfd {int fd;short events;short revents;};

要测试的条件由成员events规定，函数在相应的revents成员中返回描述字的状态。

POLLIN：普通或优先级带数据可读

POLLRDNORM：普通数据可读

POLLRDBAND：优先级带数据可读

POLLPRI：高优先级数据可读

POLLOUT：普通数据可写

POLLWRNORM：普通数据可写

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

poll识别三个类别的数据：普通、优先级带和高优先级

参数timeout指定函数返回等待多长时间，它是一个指定等待的毫秒数的正值。

INFTIM:永远等待

0：立即返回，不阻塞

>0:等待指定数目的毫秒数

服务器端：

INFTIM加了头文件#include <poll.h>和#include <sys/stropts.h>还是说无定义，后来自行定义

#include <sys/socket.h>
#include <stdio.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <errno.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/wait.h>
#include <limits.h>
#include <poll.h>
#include <sys/stropts.h>#define SIN_PORT 9999
#define BUFLEN 128
#define OPEN_MAX 100#ifndef INFTIM
#define INFTIM -1
#endifvoid str_echo(int fd);void sig_child(int signo)
{pid_t pid;int stat;while ((pid = waitpid(-1, &stat, WNOHANG)) > 0) {printf("pid %d terminated\n", pid);}}size_t readn(int fd, void *ptr, size_t n)
{char *p = ptr;size_t nleft = n;size_t nread;while (nleft > 0) {if ((nread = read(fd, p, nleft)) < 0) {if (errno == EINTR) nread = 0;else return -1;} else if (nread == 0) break;nleft -= nread;p += nread;}return n - nleft;
}size_t readline(int fd, void *ptr, size_t maxsize)
{char *p = ptr;size_t rc, n;char c;for (n = 1; n < maxsize; n++) {
again:if ((rc = read(fd, &c, 1)) == 1) {*p++ = c;if (c == '\n') break;} else if (rc == 0) {if (n == 1) return 0;else break;} else {if (errno == EINTR) goto again;return -1;}}*p = 0;return n;
}size_t writen(int fd, void *ptr, size_t n)
{char *p = ptr;size_t nleft = n,  nwriten;while (nleft > 0) {if ((nwriten = write(fd, p, nleft)) <= 0) {if (errno == EINTR) nwriten = 0;else return -1;}p += nwriten;nleft -= nwriten;}return n;
}void str_echo(int fd)
{char recvline[BUFLEN];int n;for (;;) {if ((n = readline(fd, recvline, BUFLEN)) == 0) return;printf("received buf=%s", recvline);writen(fd, recvline, n);}
}int main(int argc, char **argv)
{int listenfd, connfd, sockfd;int i, maxi, n;int nready;struct pollfd  client[OPEN_MAX];struct sockaddr_in servaddr, clientaddr;char buf[BUFLEN];socklen_t len;listenfd = socket(AF_INET, SOCK_STREAM, 0);if (listenfd < 0) {printf("socket error :%s\n", strerror(errno));        return -1;}servaddr.sin_family = AF_INET;servaddr.sin_port = htons(SIN_PORT);servaddr.sin_addr.s_addr = htonl(INADDR_ANY);signal(SIGCHLD, sig_child);if (bind(listenfd, (struct sockaddr*)&servaddr, sizeof(servaddr)) < 0) {printf("bind error:%s\n", strerror(errno));close(listenfd);return -1;}if (listen(listenfd, 3) < 0) {printf("listen error:%s\n", strerror(errno));close(listenfd);return -1;}client[0].fd = listenfd;client[0].events = POLLRDNORM;for (i = 1; i < OPEN_MAX; i++) {client[i].fd = -1;}maxi = 0;for (;;) {nready = poll(client, maxi + 1, INFTIM); if (client[0].revents & POLLRDNORM) {len = sizeof(len);connfd = accept(listenfd, (struct sockaddr*)&clientaddr, &len);for (i = 1; i < OPEN_MAX; i++) {if (client[i].fd < 0) {client[i].fd = connfd;break;}}if (i == OPEN_MAX) {printf("too many clients\n");return;}client[i].events = POLLRDNORM;if (i > maxi) maxi = i;if (--nready <= 0) continue;}for (i = 1; i <= maxi; i++) {if ((sockfd = client[i].fd) < 0) continue;if (client[i].revents & (POLLRDNORM | POLLERR)) {if ((n = readline(sockfd, buf, BUFLEN)) < 0) {if (errno == ECONNRESET) {close(sockfd);client[i].fd = -1;}} else if (n == 0) {close(sockfd);client[i].fd = -1;} else {writen(sockfd, buf, n);}}if (--nready <= 0) break;}}return 0;
}

客户端：

#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <stdio.h>#define SIN_PORT 9999
#define BUF_LEN 256
#define max(a, b) ((a) > (b) ? (a) : (b))size_t readline(int fd, void *ptr, int maxsize)
{char *p = ptr;char c;int rc;int n;for (n = 1; n < maxsize; n++) {again:if ((rc = read(fd, &c, 1)) == 1) {*p++ = c;if (c == '\n') break; } else if (rc == 0) {if (n == 1) return 0;else break;}else {if (errno == EINTR) goto again;else return -1;}}*p = 0;return n;
}size_t readn(int fd, void *ptr, size_t n)
{char *p = ptr;int nleft = n;int nread;while (nleft > 0) {if ((nread = read(fd, p, nleft)) < 0) {if (errno == EINTR) nread = 0;else return -1;} else if (nread == 0) break;nleft -= nread;p += nread;}return n - nleft;
}size_t writen(int fd, void *ptr, size_t n)
{size_t nwriten;size_t nleft = n;char *p = ptr;while (nleft > 0) {if ((nwriten = write(fd, p, nleft)) <= 0) {if (errno == EINTR) nwriten = 0;else return -1;}nleft -= nwriten;p += nwriten;}return n;
}void str_cli(FILE *file, int fd)
{char recvline[BUF_LEN], sendline[BUF_LEN];int maxfdp1;fd_set fdset;int ret;int stdineof = 0;FD_ZERO(&fdset);for(;;) {if (stdineof == 0)FD_SET(fileno(file), &fdset);FD_SET(fd, &fdset);maxfdp1 = max(fileno(file), fd) + 1;ret = select(maxfdp1, &fdset, NULL, NULL, NULL);   if (ret <= 0) {continue;}//printf("ret=%d\n", ret);if (FD_ISSET(fd, &fdset)) {if (readline(fd, recvline, BUF_LEN) == 0) {if (stdineof == 1)return;else {printf("readline error:%s\n", strerror(errno));return;}}fputs(recvline, stdout);} if (FD_ISSET(fileno(file), &fdset)) {memset(sendline, 0x00, sizeof(sendline));if (fgets(sendline, BUF_LEN, file) == NULL) {//printf("fgets error:%s\n", strerror(errno));stdineof = 1;shutdown(fd, SHUT_WR);FD_CLR(fileno(file), &fdset);continue;}//printf("len=%d\n", strlen(sendline));writen(fd, sendline, strlen(sendline));}   }
}int main(int argc, char** argv)
{struct sockaddr_in serveraddr;int sockfd;#ifndef ONLINE_JUDGE//freopen("6.4Client.c", "r", stdin);
#endifsockfd = socket(AF_INET, SOCK_STREAM, 0);if (sockfd < 0) {printf("socket error:%s\n", strerror(errno));return -1;}   serveraddr.sin_family = AF_INET;serveraddr.sin_port = htons(SIN_PORT);if (inet_pton(AF_INET, argv[1], &serveraddr.sin_addr) != 1) {printf("inet_pton error:%s\n", strerror(errno));close(sockfd);return -1;}if (connect(sockfd, (struct sockaddr*)&serveraddr, sizeof(serveraddr)) < 0) {printf("connect error:%s\n", strerror(errno));close(sockfd);return -1;}str_cli(stdin, sockfd);exit(0);}

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