operation now in process 问题；

在非阻塞模式下。连接服务器，有时候会出现服务端提示此错误；

 

解决办法：

可以把 fcntl(tcpsock,F_SETFL,O_NONBLOCK); 放到connect之后就好了！
个人觉得在connect之前就设nonblock不好。

 

此问题的官方解释：

 

man connect:

EINPROGRESS
The socket is non-blocking and the connection cannot be com-
pleted immediately. It is possible to select(2) or poll(2) for
completion by selecting the socket for writing. After select(2)
indicates writability, use getsockopt(2) to read the SO_ERROR
option at level SOL_SOCKET to determine whether connect() com-
pleted successfully (SO_ERROR is zero) or unsuccessfully
(SO_ERROR is one of the usual error codes listed here, explain-
ing the reason for the failure).

 

int
connect_nonb(int sockfd, const SA *saptr, socklen_t salen, int nsec)
{
    int     flags, n, error;
    socklen_t len;
    fd_set rset, wset;
    struct timeval tval;

    flags = Fcntl(sockfd, F_GETFL, 0);
    Fcntl(sockfd, F_SETFL, flags | O_NONBLOCK);

    error = 0;
    if ( (n = connect(sockfd, saptr, salen)) < 0)
        if (errno != EINPROGRESS)
            return (-1);

    /* Do whatever we want while the connect is taking place. */

    if (n == 0)
        goto done;               /* connect completed immediately */

    FD_ZERO(&rset);
    FD_SET(sockfd, &rset);
    wset = rset;
    tval.tv_sec = nsec;
    tval.tv_usec = 0;

    if ( (n = Select(sockfd + 1, &rset, &wset, NULL,
                    nsec ? &tval : NULL)) == 0) {
        close(sockfd);          /* timeout */
        errno = ETIMEDOUT;
        return (-1);
    }

    if (FD_ISSET(sockfd, &rset) || FD_ISSET(sockfd, &wset)) {
        len = sizeof(error);
        if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &error, &len) < 0)
            return (-1);     /* Solaris pending error */
    } else
        err_quit("select error: sockfd not set");

  done:
    Fcntl(sockfd, F_SETFL, flags);  /* restore file status flags */

    if (error) {
        close(sockfd);           /* just in case */
        errno = error;
        return (-1);
    }
    return (0);
}