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
#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
#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
#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
#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;
}
