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 > 0) {
        fd_set rSet;
        FD_ZERO(&rSet);
        FD_SET(fd, &rSet);

        struct timeval timeout;
        memset(&timeout, 0, sizeof(timeout));
        timeout.tv_sec = time;
        timeout.tv_usec = 0;
        
        int ret;
        while(1) {
            ret = select(fd+1, &rSet, NULL, NULL, &timeout);
            if(ret < 0) {
                if(errno == EINTR) continue;
                ERR_EXIT("select");
            } else if(ret == 0) {
                errno = ETIMEDOUT;
                return -1;
            } 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 > 0) {
        fd_set wSet;
        FD_ZERO(&wSet);
        FD_SET(fd, &wSet);

        struct timeval timeout;
        memset(&timeout, 0, sizeof(timeout));
        timeout.tv_sec = time;
        timeout.tv_usec = 0;
        
        int ret;
        while(1) {
            ret = select(fd+1, NULL, &wSet, NULL, &timeout);
            if(ret < 0) {
                if(errno == EINTR) continue;
                ERR_EXIT("select");
            } else if(ret == 0) {
                errno = ETIMEDOUT;
                return -1;
            } 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 > 0) {
        fd_set rSet;
        FD_ZERO(&rSet);
        FD_SET(fd, &rSet);

        struct timeval timeout;
        timeout.tv_sec = time;
        timeout.tv_usec = 0;

        int selectRet;
        do {
            selectRet = select(fd + 1, &rSet, NULL, NULL, &timeout);
        }while(selectRet < 0 && selectRet == EINTR);
        if(selectRet < 0 ) {
            return -1;
        } else if(selectRet == 0) {
            errno = ETIMEDOUT;
            return -1;
        }    
    }
    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 < 0) {
        ERR_EXIT("fcntl");
    }
    flags |= O_NONBLOCK;
    if(fcntl(fd, F_SETFL, flags) < 0) {
        ERR_EXIT("fcntl");
    }
}

void setBlockMode(int fd)
{
    int flags = fcntl(fd, F_GETFL);
    if(flags < 0) {
        ERR_EXIT("fcntl");
    }
    flags &= ~O_NONBLOCK;
    if(fcntl(fd, F_SETFL, flags) < 0) {
        ERR_EXIT("fcntl");
    }

}

int connect_timeout(int sockfd, struct sockaddrin *addr, socklen_t addrlen, int time)
{
    int ret = -1;

    if(time > 0) {
        setNonBlockMode(sockfd);
    }    
    ret = connect(sockfd, (struct sockaddr*)addr, addrlen);
    if(ret < 0 && errno == EINPROGRESS) {
        fd_set wSet;
        FD_ZERO(&wSet);
        FD_SET(sockfd, &wSet);
        
        struct timeval timeout;
        timeout.tv_sec = time;
        timeout.tv_usec = 0;
        
        int selcetRet;
        do{
            selcetRet = select(sockfd + 1, NULL, &wSet, NULL, &timeout);
        }while(selcetRet < 0 && errno == EINTR);
        if(selcetRet < 0) {
            ret = -1;
        } else if(selcetRet == 0) {
            ret = -1;
            errno = ETIMEDOUT;
        } else if(selcetRet > 0) {
            int err;
            socklen_t socklen = sizeof(err);
            int sockoptRet = getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &err, &socklen);
            if(sockoptRet == -1) {
                ret = -1;
            } 
            if(err == 0) {
                ret = 0;
            } else {
                errno = err;
                ret = -1;
            }
        }
    }
    if(time > 0) {
        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。