1 poll
A
依赖的头文件
#include <poll.h>
B
函数声明
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
|POLLRDBAND
POLLRDNORM-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监控数据中有多少文件描述符需要被监控
timeout
毫秒级等待
-1：阻塞等，#defineINFTIM -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。
ppollGNU定义了ppoll(非POSIX标准)，可以支持设置信号屏蔽字，大家可参考poll模型自行实现C/S
#define _GNU_SOURCE /* Seefeature_test_macros(7) */
#include <poll.h>
int ppoll(struct pollfd *fds, nfds_t nfds,
const struct timespec *timeout_ts, constsigset_t *sigmask);
案例说明：
Server.c
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#include<stdio.h> #include<stdlib.h> #include<string.h> #include<netinet/in.h> #include<arpa/inet.h> #include<poll.h> #include<errno.h> #include<ctype.h> #include"wrap.h" #define MAXLINE 80 #define SERV_PORT 8000 #define OPEN_MAX 1024 int main(void) { 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.c
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#include<stdio.h> #include<string.h> #include<unistd.h> #include<arpa/inet.h> #include<netinet/in.h> #include"wrap.h" #define MAXLINE 80 #define SERV_PORT 8000 int main(void) { 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"); } else { Write(STDOUT_FILENO,buf,n); } } Close(sockfd); return 0; } |
Wrap.h
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#ifndef __WRAP_H_ #define __WRAP_H_ void perr_exit(const char *s); int Accept(int fd, struct sockaddr *sa, socklen_t *salenptr); void Bind(int fd, const struct sockaddr *sa, socklen_t salen); void Connect(int fd, const struct sockaddr *sa, socklen_t salen); void Listen(int fd, int backlog); int Socket(int family, int type, int protocol); ssize_t Read(int fd, void *ptr, size_t nbytes); ssize_t Write(int fd, const void *ptr, size_t nbytes); void Close(int fd); ssize_t Readn(int fd, void *vptr, size_t n); ssize_t Writen(int fd, const void *vptr, size_t n); static ssize_t my_read(int fd, char *ptr); ssize_t Readline(int fd, void *vptr, size_t maxlen); #endif |
Wrap.c
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#include <stdlib.h> #include <errno.h> #include <sys/socket.h> void perr_exit(const char *s) { perror(s); exit(1); } int Accept(int fd, struct sockaddr *sa, socklen_t *salenptr) { int n; again: if ( (n = accept(fd, sa, salenptr)) < 0) { if ((errno == ECONNABORTED) || (errno == EINTR)) goto again; else perr_exit("accept error"); } return n; } void Bind(int fd, const struct sockaddr *sa, socklen_t salen) { if (bind(fd, sa, salen) < 0) perr_exit("bind error"); } void Connect(int fd, const struct sockaddr *sa, socklen_t salen) { if (connect(fd, sa, salen) < 0) perr_exit("connect error"); } void Listen(int fd, int backlog) { if (listen(fd, backlog) < 0) perr_exit("listen error"); } int Socket(int family, int type, int protocol) { int n; if ( (n = socket(family, type, protocol)) < 0) perr_exit("socket error"); return n; } ssize_t Read(int fd, void *ptr, size_t nbytes) { ssize_t n; again: if ( (n = read(fd, ptr, nbytes)) == -1) { if (errno == EINTR) goto again; else return -1; } return n; } ssize_t Write(int fd, const void *ptr, size_t nbytes) { ssize_t n; again: if ( (n = write(fd, ptr, nbytes)) == -1) { if (errno == EINTR) goto again; else return -1; } return n; } void Close(int fd) { if (close(fd) == -1) perr_exit("close error"); } ssize_t Readn(int fd, void *vptr, size_t n) { size_t nleft; ssize_t nread; char *ptr; ptr = vptr; nleft = n; while (nleft > 0) { if ( (nread = read(fd, ptr, nleft)) < 0) { if (errno == EINTR) nread = 0; else return -1; } else if (nread == 0) break; nleft -= nread; ptr += nread; } return n - nleft; } ssize_t Writen(int fd, const void *vptr, size_t n) { size_t nleft; ssize_t nwritten; const char *ptr; ptr = vptr; nleft = n; while (nleft > 0) { if ( (nwritten = write(fd, ptr, nleft)) <= 0) { if (nwritten < 0 && errno == EINTR) nwritten = 0; else return -1; } nleft -= nwritten; ptr += nwritten; } return n; } static ssize_t my_read(int fd, char *ptr) { static int read_cnt; static char *read_ptr; static char read_buf[100]; if (read_cnt <= 0) { again: if ( (read_cnt = read(fd, read_buf, sizeof(read_buf))) < 0) { if (errno == EINTR) goto again; return -1; } else if (read_cnt == 0) return 0; read_ptr = read_buf; } read_cnt--; *ptr = *read_ptr++; return 1; } ssize_t Readline(int fd, void *vptr, size_t maxlen) { ssize_t n, rc; char c, *ptr; ptr = vptr; for (n = 1; n < maxlen; n++) { if ( (rc = my_read(fd, &c)) == 1) { *ptr++ = c; if (c == ‘\n‘) break; } else if (rc == 0) { *ptr = 0; return n - 1; } else return -1; } *ptr = 0; return n; } |