2高并发服务器：多路IO之poll
1 poll
A 依賴的頭文件
#include <poll.h>
B 函數聲明
int poll(struct pollfd *fds, nfds_t nfds,int timeout);
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struct pollfd {
int fd; /* 文件描述符*/
short events; /* 監控的事件*/
short revents; /* 監控事件中滿足條件返回的事件*/
};
POLLIN普通或帶外優先數據可讀,即POLLRDNORM |POLLRDBAND
POLLRDNORM-數據可讀
POLLRDBAND-優先級帶數據可讀
POLLPRI 高優先級可讀數據
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POLLOUT普通或帶外數據可寫
POLLWRNORM-數據可寫
POLLWRBAND-優先級帶數據可寫
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POLLERR 發生錯誤
POLLHUP 發生掛起
POLLNVAL 描述字不是一個打開的文件
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nfds監控數據中有多少文件描述符需要被監控
timeout 毫秒級等待
-1：阻塞等，#defineINFTIM -1 Linux中沒有定義此宏
0 ：立即返回，不阻塞進程
>0：等待指定毫秒數，如當前系統時間精度不夠毫秒，向上取值
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如果不再監控某個文件描述符時，可以把pollfd中，fd設置為-1，poll不再監控此pollfd，下次返回時，把revents設置為0。
??? ppollGNU定義了ppoll(非POSIX標準)，可以支持設置信號屏蔽字，大家可參考poll模型自行實現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);
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案例說明：
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監聽普通讀事件*/ ??? 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[]數組有效元素中最大元素下標*/ ??? for ( ; ; ) { ??????? nready = poll(client, maxi+1, -1); /* 阻塞*/ ??????? if (client[0].revents & POLLRDNORM) { /* 有客戶端鏈接請求*/ ??????????? 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[]中空閑的位置，存放accept返回的connfd */ ??????????????????? break; ??????????????? } ??????????? if (i == OPEN_MAX) ??????????????? perr_exit("too many clients"); ??????????? client[i].events = POLLRDNORM; /* 設置剛剛返回的connfd，監控讀事件*/ ??????????? if (i > maxi) ??????????????? maxi = i; /* 更新client[]中最大元素下標*/ ??????????? if (--nready <= 0) ??????????????? continue; /* 沒有更多就緒事件時,繼續回到poll阻塞*/ ??????? } ??????? for (i = 1; i <= maxi; i++) { /* 檢測client[] */ ??????????? if ( (sockfd = client[i].fd) < 0) ??????????????? continue; ??????????? if (client[i].revents & (POLLRDNORM | POLLERR)) { ??????????????? if ( (n = Read(sockfd, buf, MAXLINE)) < 0) { ????????????? ??????if (errno == ECONNRESET) { /* 當收到RST標志時*/ ??????????????????????? /* 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; } |
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