socket编程（八）

1.五种I/O模型

1.阻塞I/O

2.非阻塞I/O

fcntl(fd, F_SETFL, flag|O_NONBLOCK);

忙等待，不推荐使用

3.I/O复用

4.信号驱动I/O

信号通知，有数据到来。应用进程通过信号处理程序中，调用recv函数，从内核空间拉到用户空间中。

5.异步I/O

信号接收到数据，推送到buf中。

2.select

int select (int nfds, fd_set* readfds, fd_set* writefds, fd_set* excepts, struct timeval* timeout);

void FD_CLR(int fd, fd_set* set);

int FD_ISSET(int fd, fd_set* set);

void FD_SET(int fd, fd_set* set);

void FD_ZERO(fd_set* set);

Select管理者

用select来管理多个I/O。一旦其中的一个或者多个I/O检测到我们所感兴趣的事件。

Select函数返回，返回值为检测到的事件个数

并且返回哪些I/O发生了事件

遍历这些事件，进而处理事件

param:

1.   读，写，异常集合中的文件描述符的最大值+1

2.   读集合

3.   写集合

4.   异常集合

5.   超时结构体

3.select改进回射客户端

（1）多个I/O，单进程处理

（2）服务端关闭与客户端的子进程，服务端等待到客户端read返回0；否则需要stdin输入。这样可以同时处理输入I/O，套接字I/O。

（3）标准输入I/O，网络I/O。同时检测这两种事件

#include <unistd.h>#include <sys/types.h>#include <sys/socket.h>#include <netinet/in.h>#include <arpa/inet.h>#include <signal.h>#include <stdlib.h>#include <stdio.h>#include <errno.h>#include <string.h>#define ERR_EXIT(m) \    do \    { \    perror(m); \    exit(EXIT_FAILURE); \    }while(0)    ssize_t readn(int fd, void* buf, size_t count) {size_t nleft = count;ssize_t nread;  //已经读了char* bufp = (char*)buf;while(nleft > 0) {if((nread = read(fd, bufp, nleft)) < 0) {if(errno == EINTR) continue;return -1;} else if (0 == nread) {return count - nleft;}bufp += nread;nleft -= nread;}return count;}ssize_t writen(int fd, void* buf, size_t count) {size_t nleft = count;ssize_t nwrite;char* bufp = (char*)buf;while(nleft > 0) {if((nwrite = write(fd, bufp, nleft)) < 0) {if(errno == EINTR)continue;return -1;} else if(0 == nwrite) {continue;}bufp += nwrite;nleft -= nwrite;}return count;}ssize_t recv_peek(int sockfd, void* buf, size_t len) {while(1) {int ret = recv(sockfd, buf, len, MSG_PEEK);if(-1 == ret && errno == EINTR) continue;return ret;}}//读取遇到\r\n截止，最大不能超过maxlinessize_t readline(int sockfd, void* buf, size_t maxline) {int ret;int nread;char* bufp = (char*)buf;int nleft = maxline;while(1) {ret = recv_peek(sockfd, bufp, nleft);if(ret < 0) //信号中断 return ret;if(0 == ret)  //表示对方关闭套接口 return ret;nread = ret;int i;//该缓冲区中有\n，read读走for(i=0; i<nread; i++) {if(bufp[i] == '\n') {ret = readn(sockfd, bufp, i+1);  //包括\n都读走if(ret != i+1) exit(EXIT_FAILURE);return ret;}}//没有\n，read先读走这部分，然后bufp偏移if(nread > nleft) exit(EXIT_FAILURE);nleft -= nread;ret = readn(sockfd, bufp, nread); if(ret != nread) exit(EXIT_FAILURE);bufp += nread;}return -1;}void echo_cli(int sock) {/*  char sendbuf[1024] = {0};  char recvbuf[1024] = {0};  int n;  while(fgets(sendbuf, sizeof(sendbuf), stdin) != NULL) {//将带有\n的buf发送过去  //writen(sock, sendbuf, strlen(sendbuf));  //TCP协议栈收到FIN报文writen(sock, sendbuf, 1);//TCP协议栈收到RST报文writen(sock, sendbuf+1, strlen(sendbuf)-1);//第二次发送后，会产生SIGPIPE信号  int ret = readline(sock, recvbuf, sizeof(recvbuf));if(-1 == ret) {ERR_EXIT("readline");} else if(0 == ret) {printf("client close\n");break;}  fputs(recvbuf, stdout);  memset(sendbuf, 0, sizeof(sendbuf));  memset(recvbuf, 0, sizeof(recvbuf));  }  close(sock);*/fd_set rset;FD_ZERO(&rset);int nready;int maxfd;int fd_stdin = fileno(stdin);if(fd_stdin > sock) maxfd = fd_stdin;elsemaxfd = sock;  char sendbuf[1024] = {0};  char recvbuf[1024] = {0};while(1) {FD_SET(fd_stdin, &rset);FD_SET(sock, &rset);nready = select(maxfd+1, &rset, NULL, NULL, NULL);if(-1 == nready) ERR_EXIT("select");if(0 == nready) continue;if(FD_ISSET(sock, &rset)) {int ret = readline(sock, recvbuf, sizeof(recvbuf));if(-1 == ret) {ERR_EXIT("readline");} else if(0 == ret) {printf("server close\n");break;}fputs(recvbuf, stdout);memset(sendbuf, 0, sizeof(sendbuf));memset(recvbuf, 0, sizeof(recvbuf));}if(FD_ISSET(fd_stdin, &rset)) {if(fgets(sendbuf, sizeof(sendbuf), stdin) == NULL)break;writen(sock, sendbuf, strlen(sendbuf));memset(sendbuf, 0, sizeof(sendbuf));}}close(sock);}void handle_sigpipe(int sig) {printf("recv a sig=%d\n", sig); }int main () {//signal(SIGPIPE, handle_sigpipe);signal(SIGPIPE, SIG_IGN);  int sock;if(( sock= socket(PF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0)  ERR_EXIT("socket");    sock = socket(PF_INET, SOCK_STREAM, 0);    struct sockaddr_in servaddr;  memset(&servaddr, 0, sizeof(servaddr));  servaddr.sin_family = AF_INET;  servaddr.sin_port = htons(5188);  servaddr.sin_addr.s_addr = inet_addr("127.0.0.1");    if(connect(sock, (struct sockaddr*)&servaddr, sizeof(servaddr)) < 0)  ERR_EXIT("sockect");    //获得本端ip,portstruct sockaddr_in localaddr;socklen_t addrlen= sizeof(localaddr);if(getsockname(sock,(struct sockaddr*)&localaddr, &addrlen) < 0)ERR_EXIT("getsockname");printf("ip=%s port=%d\n", inet_ntoa(localaddr.sin_addr), ntohs(localaddr.sin_port));struct sockaddr_in connaddr;socklen_t connlen = sizeof(connaddr);//通过getpeername得到对端addr,port[conn必须是已连接的套接字]getpeername(sock, (struct sockaddr*)&connaddr, &connlen);printf("ip=%s port=%d\n", inet_ntoa(connaddr.sin_addr), ntohs(connaddr.sin_port));  echo_cli(sock);  return 0;}