static int stor_cmd_receive(int socket, uint8_t *buf, int bufsz, int timeout)
{
    if((socket < 0) || (buf == RT_NULL) || (bufsz <= 0) || (timeout <= 0))
        return -RT_ERROR;

    int len = 0;
    int rc = 0;
    fd_set rset;
    struct timeval tv;

    FD_ZERO(&rset);
    FD_SET(socket, &rset);
    tv.tv_sec = timeout / 1000;
    tv.tv_usec = (timeout % 1000) * 1000;

    while(bufsz > 0)
    {
        rc = select(socket + 1, &rset, RT_NULL, RT_NULL, &tv);
        if(rc <= 0)
            break;

        rc = recv(socket, buf + len, bufsz, MSG_DONTWAIT);
        if(rc <= 0)
            break;

        len += rc;
        bufsz -= rc;

        tv.tv_sec = 3;
        tv.tv_usec = 0;
        FD_ZERO(&rset);
        FD_SET(socket, &rset);
    }

    if(rc >= 0)
        rc = len;

    return rc;
}

static int stor_cmd_fn(struct ftp_session *session, char *cmd, char *cmd_param)
{
    ....
   ......
    while(1)
    {
        int recv_bytes = stor_cmd_receive(session->port_pasv_fd, (uint8_t *)reply, 4096, timeout);
        if(recv_bytes < 0)
        {
            result = -RT_ERROR;
            break;
        }
        if(recv_bytes == 0)
            break;
        if(fwrite(reply, recv_bytes, 1, fp) != 1)
        {
            result = -RT_ERROR;
            break;
        }

        timeout = 3000;
    }
    ......
    ......
}