read,write,accept,connect 超时封装

//read操作加上超时时间。
 1 int read_timeout(int fd, void *buf, uint32_t count, int time)
 {
     if(time > ) {
         fd_set rSet;
         FD_ZERO(&rSet);
         FD_SET(fd, &rSet);

         struct timeval timeout;
         memset(&timeout, , sizeof(timeout));
         timeout.tv_sec = time;
         timeout.tv_usec = ;

         int ret;
         while() {
             ret = select(fd+, &rSet, NULL, NULL, &timeout);
             if(ret < ) {
                 if(errno == EINTR) continue;
                 ERR_EXIT("select");
             } else if(ret == ) {
                 errno = ETIMEDOUT;
                 return -;
             } else {
                 break;
             }
         }
     }
     int readNum;
     readNum = read(fd, buf, count);
     return readNum;
 }

写超时

 int write_timeout(int fd, void *buf, uint32_t count, int time)
 {
     if(time > ) {
         fd_set wSet;
         FD_ZERO(&wSet);
         FD_SET(fd, &wSet);

         struct timeval timeout;
         memset(&timeout, , sizeof(timeout));
         timeout.tv_sec = time;
         timeout.tv_usec = ;

         int ret;
         while() {
             ret = select(fd+, NULL, &wSet, NULL, &timeout);
             if(ret < ) {
                 if(errno == EINTR) continue;
                 ERR_EXIT("select");
             } else if(ret == ) {
                 errno = ETIMEDOUT;
                 return -;
             } else {
                 break;
             }
         }
     }
     int writeNum;
     writeNum = write(fd, buf, count);
     return writeNum;
 }

accept超时操作

int accept_timeout(int fd, struct sockaddrin *addr, socklen_t *addrlen, int time)
{
    int ret;
    if(time > ) {
        fd_set rSet;
        FD_ZERO(&rSet);
        FD_SET(fd, &rSet);

        struct timeval timeout;
        timeout.tv_sec = time;
        timeout.tv_usec = ;

        int selectRet;
        do {
            selectRet = select(fd + , &rSet, NULL, NULL, &timeout);
        }while(selectRet <  && selectRet == EINTR);
        if(selectRet <  ) {
            return -;
        } else if(selectRet == ) {
            errno = ETIMEDOUT;
            return -;
        }
    }
    if(addr) {
        ret = accept(fd, (struct sockaddr *)addr, addrlen);
    } else {
        ret = accept(fd, NULL, NULL);
    }
    return ret;
}

检测监听套接字是否可读，当监听套接字可读的时候，就认为连接队列发生了连接。

connect

 void setNonBlockMode(int fd)
 {
     int flags = fcntl(fd, F_GETFL);
     if(flags < ) {
         ERR_EXIT("fcntl");
     }
     flags |= O_NONBLOCK;
     if(fcntl(fd, F_SETFL, flags) < ) {
         ERR_EXIT("fcntl");
     }
 }

 void setBlockMode(int fd)
 {
     int flags = fcntl(fd, F_GETFL);
     if(flags < ) {
         ERR_EXIT("fcntl");
     }
     flags &= ~O_NONBLOCK;
     if(fcntl(fd, F_SETFL, flags) < ) {
         ERR_EXIT("fcntl");
     }

 }

 int connect_timeout(int sockfd, struct sockaddrin *addr, socklen_t addrlen, int time)
 {
     int ret = -;

     if(time > ) {
         setNonBlockMode(sockfd);
     }
     ret = connect(sockfd, (struct sockaddr*)addr, addrlen);
     if(ret <  && errno == EINPROGRESS) {
         fd_set wSet;
         FD_ZERO(&wSet);
         FD_SET(sockfd, &wSet);

         struct timeval timeout;
         timeout.tv_sec = time;
         timeout.tv_usec = ;

         int selcetRet;
         do{
             selcetRet = select(sockfd + , NULL, &wSet, NULL, &timeout);
         }while(selcetRet <  && errno == EINTR);
         if(selcetRet < ) {
             ret = -;
         } else if(selcetRet == ) {
             ret = -;
             errno = ETIMEDOUT;
         } else if(selcetRet > ) {
             int err;
             socklen_t socklen = sizeof(err);
             int sockoptRet = getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &err, &socklen);
             if(sockoptRet == -) {
                 ret = -;
             }
             if(err == ) {
                 ret = ;
             } else {
                 errno = err;
                 ret = -;
             }
         }
     }
     if(time > ) {
         setBlockMode(sockfd);
     }
     return ret;
 }

1.设置fd为非阻塞模式。

2.调用connect操作，如果网络条件很好，比如本机两个socket发生连接，会发生成功返回。

3.正常情况下，connect立即返回-1并设置errno为EINPROGRESS 表示正在连接过程中。

4.使用select检测fd是否可写。 如果检测到可写也有如下两种情况：

　　1. connect连接成功。

　　2. 产生了错误，我们就需要用getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &err, &socklen); 来判断是否发生了错误。